or any other object type with an associated meta table.
 * @param int    $object_id ID of the object metadata is for.
 * @param string $meta_key  Optional. Metadata key. If not specified, retrieve all metadata for
 *                          the specified object. Default empty string.
 * @param bool   $single    Optional. If true, return only the first value of the specified `$meta_key`.
 *                          This parameter has no effect if `$meta_key` is not specified. Default false.
 * @return mixed An array of values if `$single` is false.
 *               The value of the meta field if `$single` is true.
 *               False for an invalid `$object_id` (non-numeric, zero, or negative value),
 *               or if `$meta_type` is not specified.
 *               Null if the value does not exist.
 */
function get_metadata_raw( $meta_type, $object_id, $meta_key = '', $single = false ) {
	if ( ! $meta_type || ! is_numeric( $object_id ) ) {
		return false;
	}

	$object_id = absint( $object_id );
	if ( ! $object_id ) {
		return false;
	}

	/**
	 * Short-circuits the return value of a meta field.
	 *
	 * The dynamic portion of the hook name, `$meta_type`, refers to the meta object type
	 * (post, comment, term, user, or any other type with an associated meta table).
	 * Returning a non-null value will effectively short-circuit the function.
	 *
	 * Possible filter names include:
	 *
	 *  - `get_post_metadata`
	 *  - `get_comment_metadata`
	 *  - `get_term_metadata`
	 *  - `get_user_metadata`
	 *
	 * @since 3.1.0
	 * @since 5.5.0 Added the `$meta_type` parameter.
	 *
	 * @param mixed  $value     The value to return, either a single metadata value or an array
	 *                          of values depending on the value of `$single`. Default null.
	 * @param int    $object_id ID of the object metadata is for.
	 * @param string $meta_key  Metadata key.
	 * @param bool   $single    Whether to return only the first value of the specified `$meta_key`.
	 * @param string $meta_type Type of object metadata is for. Accepts 'post', 'comment', 'term', 'user',
	 *                          or any other object type with an associated meta table.
	 */
	$check = apply_filters( "get_{$meta_type}_metadata", null, $object_id, $meta_key, $single, $meta_type );
	if ( null !== $check ) {
		if ( $single && is_array( $check ) ) {
			return $check[0];
		} else {
			return $check;
		}
	}

	$meta_cache = wp_cache_get( $object_id, $meta_type . '_meta' );

	if ( ! $meta_cache ) {
		$meta_cache = update_meta_cache( $meta_type, array( $object_id ) );
		if ( isset( $meta_cache[ $object_id ] ) ) {
			$meta_cache = $meta_cache[ $object_id ];
		} else {
			$meta_cache = null;
		}
	}

	if ( ! $meta_key ) {
		return $meta_cache;
	}

	if ( isset( $meta_cache[ $meta_key ] ) ) {
		if ( $single ) {
			return maybe_unserialize( $meta_cache[ $meta_key ][0] );
		} else {
			return array_map( 'maybe_unserialize', $meta_cache[ $meta_key ] );
		}
	}

	return null;
}

/**
 * Retrieves default metadata value for the specified meta key and object.
 *
 * By default, an empty string is returned if `$single` is true, or an empty array
 * if it's false.
 *
 * @since 5.5.0
 *
 * @param string $meta_type Type of object metadata is for. Accepts 'post', 'comment', 'term', 'user',
 *                          or any other object type with an associated meta table.
 * @param int    $object_id ID of the object metadata is for.
 * @param string $meta_key  Metadata key.
 * @param bool   $single    Optional. If true, return only the first value of the specified `$meta_key`.
 *                          This parameter has no effect if `$meta_key` is not specified. Default false.
 * @return mixed An array of default values if `$single` is false.
 *               The default value of the meta field if `$single` is true.
 */
function get_metadata_default( $meta_type, $object_id, $meta_key, $single = false ) {
	if ( $single ) {
		$value = '';
	} else {
		$value = array();
	}

	/**
	 * Filters the default metadata value for a specified meta key and object.
	 *
	 * The dynamic portion of the hook name, `$meta_type`, refers to the meta object type
	 * (post, comment, term, user, or any other type with an associated meta table).
	 *
	 * Possible filter names include:
	 *
	 *  - `default_post_metadata`
	 *  - `default_comment_metadata`
	 *  - `default_term_metadata`
	 *  - `default_user_metadata`
	 *
	 * @since 5.5.0
	 *
	 * @param mixed  $value     The value to return, either a single metadata value or an array
	 *                          of values depending on the value of `$single`.
	 * @param int    $object_id ID of the object metadata is for.
	 * @param string $meta_key  Metadata key.
	 * @param bool   $single    Whether to return only the first value of the specified `$meta_key`.
	 * @param string $meta_type Type of object metadata is for. Accepts 'post', 'comment', 'term', 'user',
	 *                          or any other object type with an associated meta table.
	 */
	$value = apply_filters( "default_{$meta_type}_metadata", $value, $object_id, $meta_key, $single, $meta_type );

	if ( ! $single && ! wp_is_numeric_array( $value ) ) {
		$value = array( $value );
	}

	return $value;
}

/**
 * Determines if a meta field with the given key exists for the given object ID.
 *
 * @since 3.3.0
 *
 * @param string $meta_type Type of object metadata is for. Accepts 'post', 'comment', 'term', 'user',
 *                          or any other object type with an associated meta table.
 * @param int    $object_id ID of the object metadata is for.
 * @param string $meta_key  Metadata key.
 * @return bool Whether a meta field with the given key exists.
 */
function metadata_exists( $meta_type, $object_id, $meta_key ) {
	if ( ! $meta_type || ! is_numeric( $object_id ) ) {
		return false;
	}

	$object_id = absint( $object_id );
	if ( ! $object_id ) {
		return false;
	}

	/** This filter is documented in wp-includes/meta.php */
	$check = apply_filters( "get_{$meta_type}_metadata", null, $object_id, $meta_key, true, $meta_type );
	if ( null !== $check ) {
		return (bool) $check;
	}

	$meta_cache = wp_cache_get( $object_id, $meta_type . '_meta' );

	if ( ! $meta_cache ) {
		$meta_cache = update_meta_cache( $meta_type, array( $object_id ) );
		$meta_cache = $meta_cache[ $object_id ];
	}

	if ( isset( $meta_cache[ $meta_key ] ) ) {
		return true;
	}

	return false;
}

/**
 * Retrieves metadata by meta ID.
 *
 * @since 3.3.0
 *
 * @global wpdb $wpdb WordPress database abstraction object.
 *
 * @param string $meta_type Type of object metadata is for. Accepts 'post', 'comment', 'term', 'user',
 *                          or any other object type with an associated meta table.
 * @param int    $meta_id   ID for a specific meta row.
 * @return stdClass|false {
 *     Metadata object, or boolean `false` if the metadata doesn't exist.
 *
 *     @type string $meta_key   The meta key.
 *     @type mixed  $meta_value The unserialized meta value.
 *     @type string $meta_id    Optional. The meta ID when the meta type is any value except 'user'.
 *     @type string $umeta_id   Optional. The meta ID when the meta type is 'user'.
 *     @type string $post_id    Optional. The object ID when the meta type is 'post'.
 *     @type string $comment_id Optional. The object ID when the meta type is 'comment'.
 *     @type string $term_id    Optional. The object ID when the meta type is 'term'.
 *     @type string $user_id    Optional. The object ID when the meta type is 'user'.
 * }
 */
function get_metadata_by_mid( $meta_type, $meta_id ) {
	global $wpdb;

	if ( ! $meta_type || ! is_numeric( $meta_id ) || floor( $meta_id ) != $meta_id ) {
		return false;
	}

	$meta_id = (int) $meta_id;
	if ( $meta_id <= 0 ) {
		return false;
	}

	$table = _get_meta_table( $meta_type );
	if ( ! $table ) {
		return false;
	}

	/**
	 * Short-circuits the return value when fetching a meta field by meta ID.
	 *
	 * The dynamic portion of the hook name, `$meta_type`, refers to the meta object type
	 * (post, comment, term, user, or any other type with an associated meta table).
	 * Returning a non-null value will effectively short-circuit the function.
	 *
	 * Possible hook names include:
	 *
	 *  - `get_post_metadata_by_mid`
	 *  - `get_comment_metadata_by_mid`
	 *  - `get_term_metadata_by_mid`
	 *  - `get_user_metadata_by_mid`
	 *
	 * @since 5.0.0
	 *
	 * @param stdClass|null $value   The value to return.
	 * @param int           $meta_id Meta ID.
	 */
	$check = apply_filters( "get_{$meta_type}_metadata_by_mid", null, $meta_id );
	if ( null !== $check ) {
		return $check;
	}

	$id_column = ( 'user' === $meta_type ) ? 'umeta_id' : 'meta_id';

	$meta = $wpdb->get_row( $wpdb->prepare( "SELECT * FROM $table WHERE $id_column = %d", $meta_id ) );

	if ( empty( $meta ) ) {
		return false;
	}

	if ( isset( $meta->meta_value ) ) {
		$meta->meta_value = maybe_unserialize( $meta->meta_value );
	}

	return $meta;
}

/**
 * Updates metadata by meta ID.
 *
 * @since 3.3.0
 *
 * @global wpdb $wpdb WordPress database abstraction object.
 *
 * @param string       $meta_type  Type of object metadata is for. Accepts 'post', 'comment', 'term', 'user',
 *                                 or any other object type with an associated meta table.
 * @param int          $meta_id    ID for a specific meta row.
 * @param string       $meta_value Metadata value. Must be serializable if non-scalar.
 * @param string|false $meta_key   Optional. You can provide a meta key to update it. Default false.
 * @return bool True on successful update, false on failure.
 */
function update_metadata_by_mid( $meta_type, $meta_id, $meta_value, $meta_key = false ) {
	global $wpdb;

	// Make sure everything is valid.
	if ( ! $meta_type || ! is_numeric( $meta_id ) || floor( $meta_id ) != $meta_id ) {
		return false;
	}

	$meta_id = (int) $meta_id;
	if ( $meta_id <= 0 ) {
		return false;
	}

	$table = _get_meta_table( $meta_type );
	if ( ! $table ) {
		return false;
	}

	$column    = sanitize_key( $meta_type . '_id' );
	$id_column = ( 'user' === $meta_type ) ? 'umeta_id' : 'meta_id';

	/**
	 * Short-circuits updating metadata of a specific type by meta ID.
	 *
	 * The dynamic portion of the hook name, `$meta_type`, refers to the meta object type
	 * (post, comment, term, user, or any other type with an associated meta table).
	 * Returning a non-null value will effectively short-circuit the function.
	 *
	 * Possible hook names include:
	 *
	 *  - `update_post_metadata_by_mid`
	 *  - `update_comment_metadata_by_mid`
	 *  - `update_term_metadata_by_mid`
	 *  - `update_user_metadata_by_mid`
	 *
	 * @since 5.0.0
	 *
	 * @param null|bool    $check      Whether to allow updating metadata for the given type.
	 * @param int          $meta_id    Meta ID.
	 * @param mixed        $meta_value Meta value. Must be serializable if non-scalar.
	 * @param string|false $meta_key   Meta key, if provided.
	 */
	$check = apply_filters( "update_{$meta_type}_metadata_by_mid", null, $meta_id, $meta_value, $meta_key );
	if ( null !== $check ) {
		return (bool) $check;
	}

	// Fetch the meta and go on if it's found.
	$meta = get_metadata_by_mid( $meta_type, $meta_id );
	if ( $meta ) {
		$original_key = $meta->meta_key;
		$object_id    = $meta->{$column};

		/*
		 * If a new meta_key (last parameter) was specified, change the meta key,
		 * otherwise use the original key in the update statement.
		 */
		if ( false === $meta_key ) {
			$meta_key = $original_key;
		} elseif ( ! is_string( $meta_key ) ) {
			return false;
		}

		$meta_subtype = get_object_subtype( $meta_type, $object_id );

		// Sanitize the meta.
		$_meta_value = $meta_value;
		$meta_value  = sanitize_meta( $meta_key, $meta_value, $meta_type, $meta_subtype );
		$meta_value  = maybe_serialize( $meta_value );

		// Format the data query arguments.
		$data = array(
			'meta_key'   => $meta_key,
			'meta_value' => $meta_value,
		);

		// Format the where query arguments.
		$where               = array();
		$where[ $id_column ] = $meta_id;

		/** This action is documented in wp-includes/meta.php */
		do_action( "update_{$meta_type}_meta", $meta_id, $object_id, $meta_key, $_meta_value );

		if ( 'post' === $meta_type ) {
			/** This action is documented in wp-includes/meta.php */
			do_action( 'update_postmeta', $meta_id, $object_id, $meta_key, $meta_value );
		}

		// Run the update query, all fields in $data are %s, $where is a %d.
		$result = $wpdb->update( $table, $data, $where, '%s', '%d' );
		if ( ! $result ) {
			return false;
		}

		// Clear the caches.
		wp_cache_delete( $object_id, $meta_type . '_meta' );

		/** This action is documented in wp-includes/meta.php */
		do_action( "updated_{$meta_type}_meta", $meta_id, $object_id, $meta_key, $_meta_value );

		if ( 'post' === $meta_type ) {
			/** This action is documented in wp-includes/meta.php */
			do_action( 'updated_postmeta', $meta_id, $object_id, $meta_key, $meta_value );
		}

		return true;
	}

	// And if the meta was not found.
	return false;
}

/**
 * Deletes metadata by meta ID.
 *
 * @since 3.3.0
 *
 * @global wpdb $wpdb WordPress database abstraction object.
 *
 * @param string $meta_type Type of object metadata is for. Accepts 'post', 'comment', 'term', 'user',
 *                          or any other object type with an associated meta table.
 * @param int    $meta_id   ID for a specific meta row.
 * @return bool True on successful delete, false on failure.
 */
function delete_metadata_by_mid( $meta_type, $meta_id ) {
	global $wpdb;

	// Make sure everything is valid.
	if ( ! $meta_type || ! is_numeric( $meta_id ) || floor( $meta_id ) != $meta_id ) {
		return false;
	}

	$meta_id = (int) $meta_id;
	if ( $meta_id <= 0 ) {
		return false;
	}

	$table = _get_meta_table( $meta_type );
	if ( ! $table ) {
		return false;
	}

	// Object and ID columns.
	$column    = sanitize_key( $meta_type . '_id' );
	$id_column = ( 'user' === $meta_type ) ? 'umeta_id' : 'meta_id';

	/**
	 * Short-circuits deleting metadata of a specific type by meta ID.
	 *
	 * The dynamic portion of the hook name, `$meta_type`, refers to the meta object type
	 * (post, comment, term, user, or any other type with an associated meta table).
	 * Returning a non-null value will effectively short-circuit the function.
	 *
	 * Possible hook names include:
	 *
	 *  - `delete_post_metadata_by_mid`
	 *  - `delete_comment_metadata_by_mid`
	 *  - `delete_term_metadata_by_mid`
	 *  - `delete_user_metadata_by_mid`
	 *
	 * @since 5.0.0
	 *
	 * @param null|bool $delete  Whether to allow metadata deletion of the given type.
	 * @param int       $meta_id Meta ID.
	 */
	$check = apply_filters( "delete_{$meta_type}_metadata_by_mid", null, $meta_id );
	if ( null !== $check ) {
		return (bool) $check;
	}

	// Fetch the meta and go on if it's found.
	$meta = get_metadata_by_mid( $meta_type, $meta_id );
	if ( $meta ) {
		$object_id = (int) $meta->{$column};

		/** This action is documented in wp-includes/meta.php */
		do_action( "delete_{$meta_type}_meta", (array) $meta_id, $object_id, $meta->meta_key, $meta->meta_value );

		// Old-style action.
		if ( 'post' === $meta_type || 'comment' === $meta_type ) {
			/**
			 * Fires immediately before deleting post or comment metadata of a specific type.
			 *
			 * The dynamic portion of the hook name, `$meta_type`, refers to the meta
			 * object type (post or comment).
			 *
			 * Possible hook names include:
			 *
			 *  - `delete_postmeta`
			 *  - `delete_commentmeta`
			 *  - `delete_termmeta`
			 *  - `delete_usermeta`
			 *
			 * @since 3.4.0
			 *
			 * @param int $meta_id ID of the metadata entry to delete.
			 */
			do_action( "delete_{$meta_type}meta", $meta_id );
		}

		// Run the query, will return true if deleted, false otherwise.
		$result = (bool) $wpdb->delete( $table, array( $id_column => $meta_id ) );

		// Clear the caches.
		wp_cache_delete( $object_id, $meta_type . '_meta' );

		/** This action is documented in wp-includes/meta.php */
		do_action( "deleted_{$meta_type}_meta", (array) $meta_id, $object_id, $meta->meta_key, $meta->meta_value );

		// Old-style action.
		if ( 'post' === $meta_type || 'comment' === $meta_type ) {
			/**
			 * Fires immediately after deleting post or comment metadata of a specific type.
			 *
			 * The dynamic portion of the hook name, `$meta_type`, refers to the meta
			 * object type (post or comment).
			 *
			 * Possible hook names include:
			 *
			 *  - `deleted_postmeta`
			 *  - `deleted_commentmeta`
			 *  - `deleted_termmeta`
			 *  - `deleted_usermeta`
			 *
			 * @since 3.4.0
			 *
			 * @param int $meta_id Deleted metadata entry ID.
			 */
			do_action( "deleted_{$meta_type}meta", $meta_id );
		}

		return $result;

	}

	// Meta ID was not found.
	return false;
}

/**
 * Updates the metadata cache for the specified objects.
 *
 * @since 2.9.0
 *
 * @global wpdb $wpdb WordPress database abstraction object.
 *
 * @param string       $meta_type  Type of object metadata is for. Accepts 'post', 'comment', 'term', 'user',
 *                                 or any other object type with an associated meta table.
 * @param string|int[] $object_ids Array or comma delimited list of object IDs to update cache for.
 * @return array|false Metadata cache for the specified objects, or false on failure.
 */
function update_meta_cache( $meta_type, $object_ids ) {
	global $wpdb;

	if ( ! $meta_type || ! $object_ids ) {
		return false;
	}

	$table = _get_meta_table( $meta_type );
	if ( ! $table ) {
		return false;
	}

	$column = sanitize_key( $meta_type . '_id' );

	if ( ! is_array( $object_ids ) ) {
		$object_ids = preg_replace( '|[^0-9,]|', '', $object_ids );
		$object_ids = explode( ',', $object_ids );
	}

	$object_ids = array_map( 'intval', $object_ids );

	/**
	 * Short-circuits updating the metadata cache of a specific type.
	 *
	 * The dynamic portion of the hook name, `$meta_type`, refers to the meta object type
	 * (post, comment, term, user, or any other type with an associated meta table).
	 * Returning a non-null value will effectively short-circuit the function.
	 *
	 * Possible hook names include:
	 *
	 *  - `update_post_metadata_cache`
	 *  - `update_comment_metadata_cache`
	 *  - `update_term_metadata_cache`
	 *  - `update_user_metadata_cache`
	 *
	 * @since 5.0.0
	 *
	 * @param mixed $check      Whether to allow updating the meta cache of the given type.
	 * @param int[] $object_ids Array of object IDs to update the meta cache for.
	 */
	$check = apply_filters( "update_{$meta_type}_metadata_cache", null, $object_ids );
	if ( null !== $check ) {
		return (bool) $check;
	}

	$cache_key      = $meta_type . '_meta';
	$non_cached_ids = array();
	$cache          = array();
	$cache_values   = wp_cache_get_multiple( $object_ids, $cache_key );

	foreach ( $cache_values as $id => $cached_object ) {
		if ( false === $cached_object ) {
			$non_cached_ids[] = $id;
		} else {
			$cache[ $id ] = $cached_object;
		}
	}

	if ( empty( $non_cached_ids ) ) {
		return $cache;
	}

	// Get meta info.
	$id_list   = implode( ',', $non_cached_ids );
	$id_column = ( 'user' === $meta_type ) ? 'umeta_id' : 'meta_id';

	$meta_list = $wpdb->get_results( "SELECT $column, meta_key, meta_value FROM $table WHERE $column IN ($id_list) ORDER BY $id_column ASC", ARRAY_A );

	if ( ! empty( $meta_list ) ) {
		foreach ( $meta_list as $metarow ) {
			$mpid = (int) $metarow[ $column ];
			$mkey = $metarow['meta_key'];
			$mval = $metarow['meta_value'];

			// Force subkeys to be array type.
			if ( ! isset( $cache[ $mpid ] ) || ! is_array( $cache[ $mpid ] ) ) {
				$cache[ $mpid ] = array();
			}
			if ( ! isset( $cache[ $mpid ][ $mkey ] ) || ! is_array( $cache[ $mpid ][ $mkey ] ) ) {
				$cache[ $mpid ][ $mkey ] = array();
			}

			// Add a value to the current pid/key.
			$cache[ $mpid ][ $mkey ][] = $mval;
		}
	}

	$data = array();
	foreach ( $non_cached_ids as $id ) {
		if ( ! isset( $cache[ $id ] ) ) {
			$cache[ $id ] = array();
		}
		$data[ $id ] = $cache[ $id ];
	}
	wp_cache_add_multiple( $data, $cache_key );

	return $cache;
}

/**
 * Retrieves the queue for lazy-loading metadata.
 *
 * @since 4.5.0
 *
 * @return WP_Metadata_Lazyloader Metadata lazyloader queue.
 */
function wp_metadata_lazyloader() {
	static $wp_metadata_lazyloader;

	if ( null === $wp_metadata_lazyloader ) {
		$wp_metadata_lazyloader = new WP_Metadata_Lazyloader();
	}

	return $wp_metadata_lazyloader;
}

/**
 * Given a meta query, generates SQL clauses to be appended to a main query.
 *
 * @since 3.2.0
 *
 * @see WP_Meta_Query
 *
 * @param array  $meta_query        A meta query.
 * @param string $type              Type of meta.
 * @param string $primary_table     Primary database table name.
 * @param string $primary_id_column Primary ID column name.
 * @param object $context           Optional. The main query object. Default null.
 * @return string[]|false {
 *     Array containing JOIN and WHERE SQL clauses to append to the main query,
 *     or false if no table exists for the requested meta type.
 *
 *     @type string $join  SQL fragment to append to the main JOIN clause.
 *     @type string $where SQL fragment to append to the main WHERE clause.
 * }
 */
function get_meta_sql( $meta_query, $type, $primary_table, $primary_id_column, $context = null ) {
	$meta_query_obj = new WP_Meta_Query( $meta_query );
	return $meta_query_obj->get_sql( $type, $primary_table, $primary_id_column, $context );
}

/**
 * Retrieves the name of the metadata table for the specified object type.
 *
 * @since 2.9.0
 *
 * @global wpdb $wpdb WordPress database abstraction object.
 *
 * @param string $type Type of object metadata is for. Accepts 'post', 'comment', 'term', 'user',
 *                     or any other object type with an associated meta table.
 * @return string|false Metadata table name, or false if no metadata table exists
 */
function _get_meta_table( $type ) {
	global $wpdb;

	$table_name = $type . 'meta';

	if ( empty( $wpdb->$table_name ) ) {
		return false;
	}

	return $wpdb->$table_name;
}

/**
 * Determines whether a meta key is considered protected.
 *
 * @since 3.1.3
 *
 * @param string $meta_key  Metadata key.
 * @param string $meta_type Optional. Type of object metadata is for. Accepts 'post', 'comment', 'term', 'user',
 *                          or any other object type with an associated meta table. Default empty string.
 * @return bool Whether the meta key is considered protected.
 */
function is_protected_meta( $meta_key, $meta_type = '' ) {
	$sanitized_key = preg_replace( "/[^\x20-\x7E\p{L}]/", '', $meta_key );
	$protected     = strlen( $sanitized_key ) > 0 && ( '_' === $sanitized_key[0] );

	/**
	 * Filters whether a meta key is considered protected.
	 *
	 * @since 3.2.0
	 *
	 * @param bool   $protected Whether the key is considered protected.
	 * @param string $meta_key  Metadata key.
	 * @param string $meta_type Type of object metadata is for. Accepts 'post', 'comment', 'term', 'user',
	 *                          or any other object type with an associated meta table.
	 */
	return apply_filters( 'is_protected_meta', $protected, $meta_key, $meta_type );
}

/**
 * Sanitizes meta value.
 *
 * @since 3.1.3
 * @since 4.9.8 The `$object_subtype` parameter was added.
 *
 * @param string $meta_key       Metadata key.
 * @param mixed  $meta_value     Metadata value to sanitize.
 * @param string $object_type    Type of object metadata is for. Accepts 'post', 'comment', 'term', 'user',
 *                               or any other object type with an associated meta table.
 * @param string $object_subtype Optional. The subtype of the object type. Default empty string.
 * @return mixed Sanitized $meta_value.
 */
function sanitize_meta( $meta_key, $meta_value, $object_type, $object_subtype = '' ) {
	if ( ! empty( $object_subtype ) && has_filter( "sanitize_{$object_type}_meta_{$meta_key}_for_{$object_subtype}" ) ) {

		/**
		 * Filters the sanitization of a specific meta key of a specific meta type and subtype.
		 *
		 * The dynamic portions of the hook name, `$object_type`, `$meta_key`,
		 * and `$object_subtype`, refer to the metadata object type (comment, post, term, or user),
		 * the meta key value, and the object subtype respectively.
		 *
		 * @since 4.9.8
		 *
		 * @param mixed  $meta_value     Metadata value to sanitize.
		 * @param string $meta_key       Metadata key.
		 * @param string $object_type    Type of object metadata is for. Accepts 'post', 'comment', 'term', 'user',
		 *                               or any other object type with an associated meta table.
		 * @param string $object_subtype Object subtype.
		 */
		return apply_filters( "sanitize_{$object_type}_meta_{$meta_key}_for_{$object_subtype}", $meta_value, $meta_key, $object_type, $object_subtype );
	}

	/**
	 * Filters the sanitization of a specific meta key of a specific meta type.
	 *
	 * The dynamic portions of the hook name, `$meta_type`, and `$meta_key`,
	 * refer to the metadata object type (comment, post, term, or user) and the meta
	 * key value, respectively.
	 *
	 * @since 3.3.0
	 *
	 * @param mixed  $meta_value  Metadata value to sanitize.
	 * @param string $meta_key    Metadata key.
	 * @param string $object_type Type of object metadata is for. Accepts 'post', 'comment', 'term', 'user',
	 *                            or any other object type with an associated meta table.
	 */
	return apply_filters( "sanitize_{$object_type}_meta_{$meta_key}", $meta_value, $meta_key, $object_type );
}

/**
 * Registers a meta key.
 *
 * It is recommended to register meta keys for a specific combination of object type and object subtype. If passing
 * an object subtype is omitted, the meta key will be registered for the entire object type, however it can be partly
 * overridden in case a more specific meta key of the same name exists for the same object type and a subtype.
 *
 * If an object type does not support any subtypes, such as users or comments, you should commonly call this function
 * without passing a subtype.
 *
 * @since 3.3.0
 * @since 4.6.0 {@link https://core.trac.wordpress.org/ticket/35658 Modified
 *              to support an array of data to attach to registered meta keys}. Previous arguments for
 *              `$sanitize_callback` and `$auth_callback` have been folded into this array.
 * @since 4.9.8 The `$object_subtype` argument was added to the arguments array.
 * @since 5.3.0 Valid meta types expanded to include "array" and "object".
 * @since 5.5.0 The `$default` argument was added to the arguments array.
 * @since 6.4.0 The `$revisions_enabled` argument was added to the arguments array.
 * @since 6.7.0 The `label` argument was added to the arguments array.
 *
 * @param string       $object_type Type of object metadata is for. Accepts 'post', 'comment', 'term', 'user',
 *                                  or any other object type with an associated meta table.
 * @param string       $meta_key    Meta key to register.
 * @param array        $args {
 *     Data used to describe the meta key when registered.
 *
 *     @type string     $object_subtype    A subtype; e.g. if the object type is "post", the post type. If left empty,
 *                                         the meta key will be registered on the entire object type. Default empty.
 *     @type string     $type              The type of data associated with this meta key.
 *                                         Valid values are 'string', 'boolean', 'integer', 'number', 'array', and 'object'.
 *     @type string     $label             A human-readable label of the data attached to this meta key.
 *     @type string     $description       A description of the data attached to this meta key.
 *     @type bool       $single            Whether the meta key has one value per object, or an array of values per object.
 *     @type mixed      $default           The default value returned from get_metadata() if no value has been set yet.
 *                                         When using a non-single meta key, the default value is for the first entry.
 *                                         In other words, when calling get_metadata() with `$single` set to `false`,
 *                                         the default value given here will be wrapped in an array.
 *     @type callable   $sanitize_callback A function or method to call when sanitizing `$meta_key` data.
 *     @type callable   $auth_callback     Optional. A function or method to call when performing edit_post_meta,
 *                                         add_post_meta, and delete_post_meta capability checks.
 *     @type bool|array $show_in_rest      Whether data associated with this meta key can be considered public and
 *                                         should be accessible via the REST API. A custom post type must also declare
 *                                         support for custom fields for registered meta to be accessible via REST.
 *                                         When registering complex meta values this argument may optionally be an
 *                                         array with 'schema' or 'prepare_callback' keys instead of a boolean.
 *     @type bool       $revisions_enabled Whether to enable revisions support for this meta_key. Can only be used when the
 *                                         object type is 'post'.
 * }
 * @param string|array $deprecated Deprecated. Use `$args` instead.
 * @return bool True if the meta key was successfully registered in the global array, false if not.
 *              Registering a meta key with distinct sanitize and auth callbacks will fire those callbacks,
 *              but will not add to the global registry.
 */
function register_meta( $object_type, $meta_key, $args, $deprecated = null ) {
	global $wp_meta_keys;

	if ( ! is_array( $wp_meta_keys ) ) {
		$wp_meta_keys = array();
	}

	$defaults = array(
		'object_subtype'    => '',
		'type'              => 'string',
		'label'             => '',
		'description'       => '',
		'default'           => '',
		'single'            => false,
		'sanitize_callback' => null,
		'auth_callback'     => null,
		'show_in_rest'      => false,
		'revisions_enabled' => false,
	);

	// There used to be individual args for sanitize and auth callbacks.
	$has_old_sanitize_cb = false;
	$has_old_auth_cb     = false;

	if ( is_callable( $args ) ) {
		$args = array(
			'sanitize_callback' => $args,
		);

		$has_old_sanitize_cb = true;
	} else {
		$args = (array) $args;
	}

	if ( is_callable( $deprecated ) ) {
		$args['auth_callback'] = $deprecated;
		$has_old_auth_cb       = true;
	}

	/**
	 * Filters the registration arguments when registering meta.
	 *
	 * @since 4.6.0
	 *
	 * @param array  $args        Array of meta registration arguments.
	 * @param array  $defaults    Array of default arguments.
	 * @param string $object_type Type of object metadata is for. Accepts 'post', 'comment', 'term', 'user',
	 *                            or any other object type with an associated meta table.
	 * @param string $meta_key    Meta key.
	 */
	$args = apply_filters( 'register_meta_args', $args, $defaults, $object_type, $meta_key );
	unset( $defaults['default'] );
	$args = wp_parse_args( $args, $defaults );

	// Require an item schema when registering array meta.
	if ( false !== $args['show_in_rest'] && 'array' === $args['type'] ) {
		if ( ! is_array( $args['show_in_rest'] ) || ! isset( $args['show_in_rest']['schema']['items'] ) ) {
			_doing_it_wrong( __FUNCTION__, __( 'When registering an "array" meta type to show in the REST API, you must specify the schema for each array item in "show_in_rest.schema.items".' ), '5.3.0' );

			return false;
		}
	}

	$object_subtype = ! empty( $args['object_subtype'] ) ? $args['object_subtype'] : '';
	if ( $args['revisions_enabled'] ) {
		if ( 'post' !== $object_type ) {
			_doing_it_wrong( __FUNCTION__, __( 'Meta keys cannot enable revisions support unless the object type supports revisions.' ), '6.4.0' );

			return false;
		} elseif ( ! empty( $object_subtype ) && ! post_type_supports( $object_subtype, 'revisions' ) ) {
			_doing_it_wrong( __FUNCTION__, __( 'Meta keys cannot enable revisions support unless the object subtype supports revisions.' ), '6.4.0' );

			return false;
		}
	}

	// If `auth_callback` is not provided, fall back to `is_protected_meta()`.
	if ( empty( $args['auth_callback'] ) ) {
		if ( is_protected_meta( $meta_key, $object_type ) ) {
			$args['auth_callback'] = '__return_false';
		} else {
			$args['auth_callback'] = '__return_true';
		}
	}

	// Back-compat: old sanitize and auth callbacks are applied to all of an object type.
	if ( is_callable( $args['sanitize_callback'] ) ) {
		if ( ! empty( $object_subtype ) ) {
			add_filter( "sanitize_{$object_type}_meta_{$meta_key}_for_{$object_subtype}", $args['sanitize_callback'], 10, 4 );
		} else {
			add_filter( "sanitize_{$object_type}_meta_{$meta_key}", $args['sanitize_callback'], 10, 3 );
		}
	}

	if ( is_callable( $args['auth_callback'] ) ) {
		if ( ! empty( $object_subtype ) ) {
			add_filter( "auth_{$object_type}_meta_{$meta_key}_for_{$object_subtype}", $args['auth_callback'], 10, 6 );
		} else {
			add_filter( "auth_{$object_type}_meta_{$meta_key}", $args['auth_callback'], 10, 6 );
		}
	}

	if ( array_key_exists( 'default', $args ) ) {
		$schema = $args;
		if ( is_array( $args['show_in_rest'] ) && isset( $args['show_in_rest']['schema'] ) ) {
			$schema = array_merge( $schema, $args['show_in_rest']['schema'] );
		}

		$check = rest_validate_value_from_schema( $args['default'], $schema );
		if ( is_wp_error( $check ) ) {
			_doing_it_wrong( __FUNCTION__, __( 'When registering a default meta value the data must match the type provided.' ), '5.5.0' );

			return false;
		}

		if ( ! has_filter( "default_{$object_type}_metadata", 'filter_default_metadata' ) ) {
			add_filter( "default_{$object_type}_metadata", 'filter_default_metadata', 10, 5 );
		}
	}

	// Global registry only contains meta keys registered with the array of arguments added in 4.6.0.
	if ( ! $has_old_auth_cb && ! $has_old_sanitize_cb ) {
		unset( $args['object_subtype'] );

		$wp_meta_keys[ $object_type ][ $object_subtype ][ $meta_key ] = $args;

		return true;
	}

	return false;
}

/**
 * Filters into default_{$object_type}_metadata and adds in default value.
 *
 * @since 5.5.0
 *
 * @param mixed  $value     Current value passed to filter.
 * @param int    $object_id ID of the object metadata is for.
 * @param string $meta_key  Metadata key.
 * @param bool   $single    If true, return only the first value of the specified `$meta_key`.
 *                          This parameter has no effect if `$meta_key` is not specified.
 * @param string $meta_type Type of object metadata is for. Accepts 'post', 'comment', 'term', 'user',
 *                          or any other object type with an associated meta table.
 * @return mixed An array of default values if `$single` is false.
 *               The default value of the meta field if `$single` is true.
 */
function filter_default_metadata( $value, $object_id, $meta_key, $single, $meta_type ) {
	global $wp_meta_keys;

	if ( wp_installing() ) {
		return $value;
	}

	if ( ! is_array( $wp_meta_keys ) || ! isset( $wp_meta_keys[ $meta_type ] ) ) {
		return $value;
	}

	$defaults = array();
	foreach ( $wp_meta_keys[ $meta_type ] as $sub_type => $meta_data ) {
		foreach ( $meta_data as $_meta_key => $args ) {
			if ( $_meta_key === $meta_key && array_key_exists( 'default', $args ) ) {
				$defaults[ $sub_type ] = $args;
			}
		}
	}

	if ( ! $defaults ) {
		return $value;
	}

	// If this meta type does not have subtypes, then the default is keyed as an empty string.
	if ( isset( $defaults[''] ) ) {
		$metadata = $defaults[''];
	} else {
		$sub_type = get_object_subtype( $meta_type, $object_id );
		if ( ! isset( $defaults[ $sub_type ] ) ) {
			return $value;
		}
		$metadata = $defaults[ $sub_type ];
	}

	if ( $single ) {
		$value = $metadata['default'];
	} else {
		$value = array( $metadata['default'] );
	}

	return $value;
}

/**
 * Checks if a meta key is registered.
 *
 * @since 4.6.0
 * @since 4.9.8 The `$object_subtype` parameter was added.
 *
 * @param string $object_type    Type of object metadata is for. Accepts 'post', 'comment', 'term', 'user',
 *                               or any other object type with an associated meta table.
 * @param string $meta_key       Metadata key.
 * @param string $object_subtype Optional. The subtype of the object type. Default empty string.
 * @return bool True if the meta key is registered to the object type and, if provided,
 *              the object subtype. False if not.
 */
function registered_meta_key_exists( $object_type, $meta_key, $object_subtype = '' ) {
	$meta_keys = get_registered_meta_keys( $object_type, $object_subtype );

	return isset( $meta_keys[ $meta_key ] );
}

/**
 * Unregisters a meta key from the list of registered keys.
 *
 * @since 4.6.0
 * @since 4.9.8 The `$object_subtype` parameter was added.
 *
 * @param string $object_type    Type of object metadata is for. Accepts 'post', 'comment', 'term', 'user',
 *                               or any other object type with an associated meta table.
 * @param string $meta_key       Metadata key.
 * @param string $object_subtype Optional. The subtype of the object type. Default empty string.
 * @return bool True if successful. False if the meta key was not registered.
 */
function unregister_meta_key( $object_type, $meta_key, $object_subtype = '' ) {
	global $wp_meta_keys;

	if ( ! registered_meta_key_exists( $object_type, $meta_key, $object_subtype ) ) {
		return false;
	}

	$args = $wp_meta_keys[ $object_type ][ $object_subtype ][ $meta_key ];

	if ( isset( $args['sanitize_callback'] ) && is_callable( $args['sanitize_callback'] ) ) {
		if ( ! empty( $object_subtype ) ) {
			remove_filter( "sanitize_{$object_type}_meta_{$meta_key}_for_{$object_subtype}", $args['sanitize_callback'] );
		} else {
			remove_filter( "sanitize_{$object_type}_meta_{$meta_key}", $args['sanitize_callback'] );
		}
	}

	if ( isset( $args['auth_callback'] ) && is_callable( $args['auth_callback'] ) ) {
		if ( ! empty( $object_subtype ) ) {
			remove_filter( "auth_{$object_type}_meta_{$meta_key}_for_{$object_subtype}", $args['auth_callback'] );
		} else {
			remove_filter( "auth_{$object_type}_meta_{$meta_key}", $args['auth_callback'] );
		}
	}

	unset( $wp_meta_keys[ $object_type ][ $object_subtype ][ $meta_key ] );

	// Do some clean up.
	if ( empty( $wp_meta_keys[ $object_type ][ $object_subtype ] ) ) {
		unset( $wp_meta_keys[ $object_type ][ $object_subtype ] );
	}
	if ( empty( $wp_meta_keys[ $object_type ] ) ) {
		unset( $wp_meta_keys[ $object_type ] );
	}

	return true;
}

/**
 * Retrieves a list of registered metadata args for an object type, keyed by their meta keys.
 *
 * @since 4.6.0
 * @since 4.9.8 The `$object_subtype` parameter was added.
 *
 * @param string $object_type    Type of object metadata is for. Accepts 'post', 'comment', 'term', 'user',
 *                               or any other object type with an associated meta table.
 * @param string $object_subtype Optional. The subtype of the object type. Default empty string.
 * @return array[] List of registered metadata args, keyed by their meta keys.
 */
function get_registered_meta_keys( $object_type, $object_subtype = '' ) {
	global $wp_meta_keys;

	if ( ! is_array( $wp_meta_keys ) || ! isset( $wp_meta_keys[ $object_type ] ) || ! isset( $wp_meta_keys[ $object_type ][ $object_subtype ] ) ) {
		return array();
	}

	return $wp_meta_keys[ $object_type ][ $object_subtype ];
}

/**
 * Retrieves registered metadata for a specified object.
 *
 * The results include both meta that is registered specifically for the
 * object's subtype and meta that is registered for the entire object type.
 *
 * @since 4.6.0
 *
 * @param string $object_type Type of object metadata is for. Accepts 'post', 'comment', 'term', 'user',
 *                            or any other object type with an associated meta table.
 * @param int    $object_id   ID of the object the metadata is for.
 * @param string $meta_key    Optional. Registered metadata key. If not specified, retrieve all registered
 *                            metadata for the specified object.
 * @return mixed A single value or array of values for a key if specified. An array of all registered keys
 *               and values for an object ID if not. False if a given $meta_key is not registered.
 */
function get_registered_metadata( $object_type, $object_id, $meta_key = '' ) {
	$object_subtype = get_object_subtype( $object_type, $object_id );

	if ( ! empty( $meta_key ) ) {
		if ( ! empty( $object_subtype ) && ! registered_meta_key_exists( $object_type, $meta_key, $object_subtype ) ) {
			$object_subtype = '';
		}

		if ( ! registered_meta_key_exists( $object_type, $meta_key, $object_subtype ) ) {
			return false;
		}

		$meta_keys     = get_registered_meta_keys( $object_type, $object_subtype );
		$meta_key_data = $meta_keys[ $meta_key ];

		$data = get_metadata( $object_type, $object_id, $meta_key, $meta_key_data['single'] );

		return $data;
	}

	$data = get_metadata( $object_type, $object_id );
	if ( ! $data ) {
		return array();
	}

	$meta_keys = get_registered_meta_keys( $object_type );
	if ( ! empty( $object_subtype ) ) {
		$meta_keys = array_merge( $meta_keys, get_registered_meta_keys( $object_type, $object_subtype ) );
	}

	return array_intersect_key( $data, $meta_keys );
}

/**
 * Filters out `register_meta()` args based on an allowed list.
 *
 * `register_meta()` args may change over time, so requiring the allowed list
 * to be explicitly turned off is a warranty seal of sorts.
 *
 * @access private
 * @since 5.5.0
 *
 * @param array $args         Arguments from `register_meta()`.
 * @param array $default_args Default arguments for `register_meta()`.
 * @return array Filtered arguments.
 */
function _wp_register_meta_args_allowed_list( $args, $default_args ) {
	return array_intersect_key( $args, $default_args );
}

/**
 * Returns the object subtype for a given object ID of a specific type.
 *
 * @since 4.9.8
 *
 * @param string $object_type Type of object metadata is for. Accepts 'post', 'comment', 'term', 'user',
 *                            or any other object type with an associated meta table.
 * @param int    $object_id   ID of the object to retrieve its subtype.
 * @return string The object subtype or an empty string if unspecified subtype.
 */
function get_object_subtype( $object_type, $object_id ) {
	$object_id      = (int) $object_id;
	$object_subtype = '';

	switch ( $object_type ) {
		case 'post':
			$post_type = get_post_type( $object_id );

			if ( ! empty( $post_type ) ) {
				$object_subtype = $post_type;
			}
			break;

		case 'term':
			$term = get_term( $object_id );
			if ( ! $term instanceof WP_Term ) {
				break;
			}

			$object_subtype = $term->taxonomy;
			break;

		case 'comment':
			$comment = get_comment( $object_id );
			if ( ! $comment ) {
				break;
			}

			$object_subtype = 'comment';
			break;

		case 'user':
			$user = get_user_by( 'id', $object_id );
			if ( ! $user ) {
				break;
			}

			$object_subtype = 'user';
			break;
	}

	/**
	 * Filters the object subtype identifier for a non-standard object type.
	 *
	 * The dynamic portion of the hook name, `$object_type`, refers to the meta object type
	 * (post, comment, term, user, or any other type with an associated meta table).
	 *
	 * Possible hook names include:
	 *
	 *  - `get_object_subtype_post`
	 *  - `get_object_subtype_comment`
	 *  - `get_object_subtype_term`
	 *  - `get_object_subtype_user`
	 *
	 * @since 4.9.8
	 *
	 * @param string $object_subtype Empty string to override.
	 * @param int    $object_id      ID of the object to get the subtype for.
	 */
	return apply_filters( "get_object_subtype_{$object_type}", $object_subtype, $object_id );
}
ULT_TRANSPORTS;
		}

		self::$transports[$transport] = $transport;
	}

	/**
	 * Get the fully qualified class name (FQCN) for a working transport.
	 *
	 * @param array<string, bool> $capabilities Optional. Associative array of capabilities to test against, i.e. `['<capability>' => true]`.
	 * @return string FQCN of the transport to use, or an empty string if no transport was
	 *                found which provided the requested capabilities.
	 */
	protected static function get_transport_class(array $capabilities = []) {
		// Caching code, don't bother testing coverage.
		// @codeCoverageIgnoreStart
		// Array of capabilities as a string to be used as an array key.
		ksort($capabilities);
		$cap_string = serialize($capabilities);

		// Don't search for a transport if it's already been done for these $capabilities.
		if (isset(self::$transport[$cap_string])) {
			return self::$transport[$cap_string];
		}

		// Ensure we will not run this same check again later on.
		self::$transport[$cap_string] = '';
		// @codeCoverageIgnoreEnd

		if (empty(self::$transports)) {
			self::$transports = self::DEFAULT_TRANSPORTS;
		}

		// Find us a working transport.
		foreach (self::$transports as $class) {
			if (!class_exists($class)) {
				continue;
			}

			$result = $class::test($capabilities);
			if ($result === true) {
				self::$transport[$cap_string] = $class;
				break;
			}
		}

		return self::$transport[$cap_string];
	}

	/**
	 * Get a working transport.
	 *
	 * @param array<string, bool> $capabilities Optional. Associative array of capabilities to test against, i.e. `['<capability>' => true]`.
	 * @return \WpOrg\Requests\Transport
	 * @throws \WpOrg\Requests\Exception If no valid transport is found (`notransport`).
	 */
	protected static function get_transport(array $capabilities = []) {
		$class = self::get_transport_class($capabilities);

		if ($class === '') {
			throw new Exception('No working transports found', 'notransport', self::$transports);
		}

		return new $class();
	}

	/**
	 * Checks to see if we have a transport for the capabilities requested.
	 *
	 * Supported capabilities can be found in the {@see \WpOrg\Requests\Capability}
	 * interface as constants.
	 *
	 * Example usage:
	 * `Requests::has_capabilities([Capability::SSL => true])`.
	 *
	 * @param array<string, bool> $capabilities Optional. Associative array of capabilities to test against, i.e. `['<capability>' => true]`.
	 * @return bool Whether the transport has the requested capabilities.
	 */
	public static function has_capabilities(array $capabilities = []) {
		return self::get_transport_class($capabilities) !== '';
	}

	/**#@+
	 * @see \WpOrg\Requests\Requests::request()
	 * @param string $url
	 * @param array $headers
	 * @param array $options
	 * @return \WpOrg\Requests\Response
	 */
	/**
	 * Send a GET request
	 */
	public static function get($url, $headers = [], $options = []) {
		return self::request($url, $headers, null, self::GET, $options);
	}

	/**
	 * Send a HEAD request
	 */
	public static function head($url, $headers = [], $options = []) {
		return self::request($url, $headers, null, self::HEAD, $options);
	}

	/**
	 * Send a DELETE request
	 */
	public static function delete($url, $headers = [], $options = []) {
		return self::request($url, $headers, null, self::DELETE, $options);
	}

	/**
	 * Send a TRACE request
	 */
	public static function trace($url, $headers = [], $options = []) {
		return self::request($url, $headers, null, self::TRACE, $options);
	}
	/**#@-*/

	/**#@+
	 * @see \WpOrg\Requests\Requests::request()
	 * @param string $url
	 * @param array $headers
	 * @param array $data
	 * @param array $options
	 * @return \WpOrg\Requests\Response
	 */
	/**
	 * Send a POST request
	 */
	public static function post($url, $headers = [], $data = [], $options = []) {
		return self::request($url, $headers, $data, self::POST, $options);
	}
	/**
	 * Send a PUT request
	 */
	public static function put($url, $headers = [], $data = [], $options = []) {
		return self::request($url, $headers, $data, self::PUT, $options);
	}

	/**
	 * Send an OPTIONS request
	 */
	public static function options($url, $headers = [], $data = [], $options = []) {
		return self::request($url, $headers, $data, self::OPTIONS, $options);
	}

	/**
	 * Send a PATCH request
	 *
	 * Note: Unlike {@see \WpOrg\Requests\Requests::post()} and {@see \WpOrg\Requests\Requests::put()},
	 * `$headers` is required, as the specification recommends that should send an ETag
	 *
	 * @link https://tools.ietf.org/html/rfc5789
	 */
	public static function patch($url, $headers, $data = [], $options = []) {
		return self::request($url, $headers, $data, self::PATCH, $options);
	}
	/**#@-*/

	/**
	 * Main interface for HTTP requests
	 *
	 * This method initiates a request and sends it via a transport before
	 * parsing.
	 *
	 * The `$options` parameter takes an associative array with the following
	 * options:
	 *
	 * - `timeout`: How long should we wait for a response?
	 *    Note: for cURL, a minimum of 1 second applies, as DNS resolution
	 *    operates at second-resolution only.
	 *    (float, seconds with a millisecond precision, default: 10, example: 0.01)
	 * - `connect_timeout`: How long should we wait while trying to connect?
	 *    (float, seconds with a millisecond precision, default: 10, example: 0.01)
	 * - `useragent`: Useragent to send to the server
	 *    (string, default: php-requests/$version)
	 * - `follow_redirects`: Should we follow 3xx redirects?
	 *    (boolean, default: true)
	 * - `redirects`: How many times should we redirect before erroring?
	 *    (integer, default: 10)
	 * - `blocking`: Should we block processing on this request?
	 *    (boolean, default: true)
	 * - `filename`: File to stream the body to instead.
	 *    (string|boolean, default: false)
	 * - `auth`: Authentication handler or array of user/password details to use
	 *    for Basic authentication
	 *    (\WpOrg\Requests\Auth|array|boolean, default: false)
	 * - `proxy`: Proxy details to use for proxy by-passing and authentication
	 *    (\WpOrg\Requests\Proxy|array|string|boolean, default: false)
	 * - `max_bytes`: Limit for the response body size.
	 *    (integer|boolean, default: false)
	 * - `idn`: Enable IDN parsing
	 *    (boolean, default: true)
	 * - `transport`: Custom transport. Either a class name, or a
	 *    transport object. Defaults to the first working transport from
	 *    {@see \WpOrg\Requests\Requests::getTransport()}
	 *    (string|\WpOrg\Requests\Transport, default: {@see \WpOrg\Requests\Requests::getTransport()})
	 * - `hooks`: Hooks handler.
	 *    (\WpOrg\Requests\HookManager, default: new WpOrg\Requests\Hooks())
	 * - `verify`: Should we verify SSL certificates? Allows passing in a custom
	 *    certificate file as a string. (Using true uses the system-wide root
	 *    certificate store instead, but this may have different behaviour
	 *    across transports.)
	 *    (string|boolean, default: certificates/cacert.pem)
	 * - `verifyname`: Should we verify the common name in the SSL certificate?
	 *    (boolean, default: true)
	 * - `data_format`: How should we send the `$data` parameter?
	 *    (string, one of 'query' or 'body', default: 'query' for
	 *    HEAD/GET/DELETE, 'body' for POST/PUT/OPTIONS/PATCH)
	 *
	 * @param string|Stringable $url URL to request
	 * @param array $headers Extra headers to send with the request
	 * @param array|null $data Data to send either as a query string for GET/HEAD requests, or in the body for POST requests
	 * @param string $type HTTP request type (use Requests constants)
	 * @param array $options Options for the request (see description for more information)
	 * @return \WpOrg\Requests\Response
	 *
	 * @throws \WpOrg\Requests\Exception\InvalidArgument When the passed $url argument is not a string or Stringable.
	 * @throws \WpOrg\Requests\Exception\InvalidArgument When the passed $type argument is not a string.
	 * @throws \WpOrg\Requests\Exception\InvalidArgument When the passed $options argument is not an array.
	 * @throws \WpOrg\Requests\Exception On invalid URLs (`nonhttp`)
	 */
	public static function request($url, $headers = [], $data = [], $type = self::GET, $options = []) {
		if (InputValidator::is_string_or_stringable($url) === false) {
			throw InvalidArgument::create(1, '$url', 'string|Stringable', gettype($url));
		}

		if (is_string($type) === false) {
			throw InvalidArgument::create(4, '$type', 'string', gettype($type));
		}

		if (is_array($options) === false) {
			throw InvalidArgument::create(5, '$options', 'array', gettype($options));
		}

		if (empty($options['type'])) {
			$options['type'] = $type;
		}

		$options = array_merge(self::get_default_options(), $options);

		self::set_defaults($url, $headers, $data, $type, $options);

		$options['hooks']->dispatch('requests.before_request', [&$url, &$headers, &$data, &$type, &$options]);

		if (!empty($options['transport'])) {
			$transport = $options['transport'];

			if (is_string($options['transport'])) {
				$transport = new $transport();
			}
		} else {
			$need_ssl     = (stripos($url, 'https://') === 0);
			$capabilities = [Capability::SSL => $need_ssl];
			$transport    = self::get_transport($capabilities);
		}

		$response = $transport->request($url, $headers, $data, $options);

		$options['hooks']->dispatch('requests.before_parse', [&$response, $url, $headers, $data, $type, $options]);

		return self::parse_response($response, $url, $headers, $data, $options);
	}

	/**
	 * Send multiple HTTP requests simultaneously
	 *
	 * The `$requests` parameter takes an associative or indexed array of
	 * request fields. The key of each request can be used to match up the
	 * request with the returned data, or with the request passed into your
	 * `multiple.request.complete` callback.
	 *
	 * The request fields value is an associative array with the following keys:
	 *
	 * - `url`: Request URL Same as the `$url` parameter to
	 *    {@see \WpOrg\Requests\Requests::request()}
	 *    (string, required)
	 * - `headers`: Associative array of header fields. Same as the `$headers`
	 *    parameter to {@see \WpOrg\Requests\Requests::request()}
	 *    (array, default: `array()`)
	 * - `data`: Associative array of data fields or a string. Same as the
	 *    `$data` parameter to {@see \WpOrg\Requests\Requests::request()}
	 *    (array|string, default: `array()`)
	 * - `type`: HTTP request type (use \WpOrg\Requests\Requests constants). Same as the `$type`
	 *    parameter to {@see \WpOrg\Requests\Requests::request()}
	 *    (string, default: `\WpOrg\Requests\Requests::GET`)
	 * - `cookies`: Associative array of cookie name to value, or cookie jar.
	 *    (array|\WpOrg\Requests\Cookie\Jar)
	 *
	 * If the `$options` parameter is specified, individual requests will
	 * inherit options from it. This can be used to use a single hooking system,
	 * or set all the types to `\WpOrg\Requests\Requests::POST`, for example.
	 *
	 * In addition, the `$options` parameter takes the following global options:
	 *
	 * - `complete`: A callback for when a request is complete. Takes two
	 *    parameters, a \WpOrg\Requests\Response/\WpOrg\Requests\Exception reference, and the
	 *    ID from the request array (Note: this can also be overridden on a
	 *    per-request basis, although that's a little silly)
	 *    (callback)
	 *
	 * @param array $requests Requests data (see description for more information)
	 * @param array $options Global and default options (see {@see \WpOrg\Requests\Requests::request()})
	 * @return array Responses (either \WpOrg\Requests\Response or a \WpOrg\Requests\Exception object)
	 *
	 * @throws \WpOrg\Requests\Exception\InvalidArgument When the passed $requests argument is not an array or iterable object with array access.
	 * @throws \WpOrg\Requests\Exception\InvalidArgument When the passed $options argument is not an array.
	 */
	public static function request_multiple($requests, $options = []) {
		if (InputValidator::has_array_access($requests) === false || InputValidator::is_iterable($requests) === false) {
			throw InvalidArgument::create(1, '$requests', 'array|ArrayAccess&Traversable', gettype($requests));
		}

		if (is_array($options) === false) {
			throw InvalidArgument::create(2, '$options', 'array', gettype($options));
		}

		$options = array_merge(self::get_default_options(true), $options);

		if (!empty($options['hooks'])) {
			$options['hooks']->register('transport.internal.parse_response', [static::class, 'parse_multiple']);
			if (!empty($options['complete'])) {
				$options['hooks']->register('multiple.request.complete', $options['complete']);
			}
		}

		foreach ($requests as $id => &$request) {
			if (!isset($request['headers'])) {
				$request['headers'] = [];
			}

			if (!isset($request['data'])) {
				$request['data'] = [];
			}

			if (!isset($request['type'])) {
				$request['type'] = self::GET;
			}

			if (!isset($request['options'])) {
				$request['options']         = $options;
				$request['options']['type'] = $request['type'];
			} else {
				if (empty($request['options']['type'])) {
					$request['options']['type'] = $request['type'];
				}

				$request['options'] = array_merge($options, $request['options']);
			}

			self::set_defaults($request['url'], $request['headers'], $request['data'], $request['type'], $request['options']);

			// Ensure we only hook in once
			if ($request['options']['hooks'] !== $options['hooks']) {
				$request['options']['hooks']->register('transport.internal.parse_response', [static::class, 'parse_multiple']);
				if (!empty($request['options']['complete'])) {
					$request['options']['hooks']->register('multiple.request.complete', $request['options']['complete']);
				}
			}
		}

		unset($request);

		if (!empty($options['transport'])) {
			$transport = $options['transport'];

			if (is_string($options['transport'])) {
				$transport = new $transport();
			}
		} else {
			$transport = self::get_transport();
		}

		$responses = $transport->request_multiple($requests, $options);

		foreach ($responses as $id => &$response) {
			// If our hook got messed with somehow, ensure we end up with the
			// correct response
			if (is_string($response)) {
				$request = $requests[$id];
				self::parse_multiple($response, $request);
				$request['options']['hooks']->dispatch('multiple.request.complete', [&$response, $id]);
			}
		}

		return $responses;
	}

	/**
	 * Get the default options
	 *
	 * @see \WpOrg\Requests\Requests::request() for values returned by this method
	 * @param boolean $multirequest Is this a multirequest?
	 * @return array Default option values
	 */
	protected static function get_default_options($multirequest = false) {
		$defaults           = static::OPTION_DEFAULTS;
		$defaults['verify'] = self::$certificate_path;

		if ($multirequest !== false) {
			$defaults['complete'] = null;
		}

		return $defaults;
	}

	/**
	 * Get default certificate path.
	 *
	 * @return string Default certificate path.
	 */
	public static function get_certificate_path() {
		return self::$certificate_path;
	}

	/**
	 * Set default certificate path.
	 *
	 * @param string|Stringable|bool $path Certificate path, pointing to a PEM file.
	 *
	 * @throws \WpOrg\Requests\Exception\InvalidArgument When the passed $url argument is not a string, Stringable or boolean.
	 */
	public static function set_certificate_path($path) {
		if (InputValidator::is_string_or_stringable($path) === false && is_bool($path) === false) {
			throw InvalidArgument::create(1, '$path', 'string|Stringable|bool', gettype($path));
		}

		self::$certificate_path = $path;
	}

	/**
	 * Set the default values
	 *
	 * The $options parameter is updated with the results.
	 *
	 * @param string $url URL to request
	 * @param array $headers Extra headers to send with the request
	 * @param array|null $data Data to send either as a query string for GET/HEAD requests, or in the body for POST requests
	 * @param string $type HTTP request type
	 * @param array $options Options for the request
	 * @return void
	 *
	 * @throws \WpOrg\Requests\Exception When the $url is not an http(s) URL.
	 */
	protected static function set_defaults(&$url, &$headers, &$data, &$type, &$options) {
		if (!preg_match('/^http(s)?:\/\//i', $url, $matches)) {
			throw new Exception('Only HTTP(S) requests are handled.', 'nonhttp', $url);
		}

		if (empty($options['hooks'])) {
			$options['hooks'] = new Hooks();
		}

		if (is_array($options['auth'])) {
			$options['auth'] = new Basic($options['auth']);
		}

		if ($options['auth'] !== false) {
			$options['auth']->register($options['hooks']);
		}

		if (is_string($options['proxy']) || is_array($options['proxy'])) {
			$options['proxy'] = new Http($options['proxy']);
		}

		if ($options['proxy'] !== false) {
			$options['proxy']->register($options['hooks']);
		}

		if (is_array($options['cookies'])) {
			$options['cookies'] = new Jar($options['cookies']);
		} elseif (empty($options['cookies'])) {
			$options['cookies'] = new Jar();
		}

		if ($options['cookies'] !== false) {
			$options['cookies']->register($options['hooks']);
		}

		if ($options['idn'] !== false) {
			$iri       = new Iri($url);
			$iri->host = IdnaEncoder::encode($iri->ihost);
			$url       = $iri->uri;
		}

		// Massage the type to ensure we support it.
		$type = strtoupper($type);

		if (!isset($options['data_format'])) {
			if (in_array($type, [self::HEAD, self::GET, self::DELETE], true)) {
				$options['data_format'] = 'query';
			} else {
				$options['data_format'] = 'body';
			}
		}
	}

	/**
	 * HTTP response parser
	 *
	 * @param string $headers Full response text including headers and body
	 * @param string $url Original request URL
	 * @param array $req_headers Original $headers array passed to {@link request()}, in case we need to follow redirects
	 * @param array $req_data Original $data array passed to {@link request()}, in case we need to follow redirects
	 * @param array $options Original $options array passed to {@link request()}, in case we need to follow redirects
	 * @return \WpOrg\Requests\Response
	 *
	 * @throws \WpOrg\Requests\Exception On missing head/body separator (`requests.no_crlf_separator`)
	 * @throws \WpOrg\Requests\Exception On missing head/body separator (`noversion`)
	 * @throws \WpOrg\Requests\Exception On missing head/body separator (`toomanyredirects`)
	 */
	protected static function parse_response($headers, $url, $req_headers, $req_data, $options) {
		$return = new Response();
		if (!$options['blocking']) {
			return $return;
		}

		$return->raw  = $headers;
		$return->url  = (string) $url;
		$return->body = '';

		if (!$options['filename']) {
			$pos = strpos($headers, "\r\n\r\n");
			if ($pos === false) {
				// Crap!
				throw new Exception('Missing header/body separator', 'requests.no_crlf_separator');
			}

			$headers = substr($return->raw, 0, $pos);
			// Headers will always be separated from the body by two new lines - `\n\r\n\r`.
			$body = substr($return->raw, $pos + 4);
			if (!empty($body)) {
				$return->body = $body;
			}
		}

		// Pretend CRLF = LF for compatibility (RFC 2616, section 19.3)
		$headers = str_replace("\r\n", "\n", $headers);
		// Unfold headers (replace [CRLF] 1*( SP | HT ) with SP) as per RFC 2616 (section 2.2)
		$headers = preg_replace('/\n[ \t]/', ' ', $headers);
		$headers = explode("\n", $headers);
		preg_match('#^HTTP/(1\.\d)[ \t]+(\d+)#i', array_shift($headers), $matches);
		if (empty($matches)) {
			throw new Exception('Response could not be parsed', 'noversion', $headers);
		}

		$return->protocol_version = (float) $matches[1];
		$return->status_code      = (int) $matches[2];
		if ($return->status_code >= 200 && $return->status_code < 300) {
			$return->success = true;
		}

		foreach ($headers as $header) {
			list($key, $value) = explode(':', $header, 2);
			$value             = trim($value);
			preg_replace('#(\s+)#i', ' ', $value);
			$return->headers[$key] = $value;
		}

		if (isset($return->headers['transfer-encoding'])) {
			$return->body = self::decode_chunked($return->body);
			unset($return->headers['transfer-encoding']);
		}

		if (isset($return->headers['content-encoding'])) {
			$return->body = self::decompress($return->body);
		}

		//fsockopen and cURL compatibility
		if (isset($return->headers['connection'])) {
			unset($return->headers['connection']);
		}

		$options['hooks']->dispatch('requests.before_redirect_check', [&$return, $req_headers, $req_data, $options]);

		if ($return->is_redirect() && $options['follow_redirects'] === true) {
			if (isset($return->headers['location']) && $options['redirected'] < $options['redirects']) {
				if ($return->status_code === 303) {
					$options['type'] = self::GET;
				}

				$options['redirected']++;
				$location = $return->headers['location'];
				if (strpos($location, 'http://') !== 0 && strpos($location, 'https://') !== 0) {
					// relative redirect, for compatibility make it absolute
					$location = Iri::absolutize($url, $location);
					$location = $location->uri;
				}

				$hook_args = [
					&$location,
					&$req_headers,
					&$req_data,
					&$options,
					$return,
				];
				$options['hooks']->dispatch('requests.before_redirect', $hook_args);
				$redirected            = self::request($location, $req_headers, $req_data, $options['type'], $options);
				$redirected->history[] = $return;
				return $redirected;
			} elseif ($options['redirected'] >= $options['redirects']) {
				throw new Exception('Too many redirects', 'toomanyredirects', $return);
			}
		}

		$return->redirects = $options['redirected'];

		$options['hooks']->dispatch('requests.after_request', [&$return, $req_headers, $req_data, $options]);
		return $return;
	}

	/**
	 * Callback for `transport.internal.parse_response`
	 *
	 * Internal use only. Converts a raw HTTP response to a \WpOrg\Requests\Response
	 * while still executing a multiple request.
	 *
	 * `$response` is either set to a \WpOrg\Requests\Response instance, or a \WpOrg\Requests\Exception object
	 *
	 * @param string $response Full response text including headers and body (will be overwritten with Response instance)
	 * @param array $request Request data as passed into {@see \WpOrg\Requests\Requests::request_multiple()}
	 * @return void
	 */
	public static function parse_multiple(&$response, $request) {
		try {
			$url      = $request['url'];
			$headers  = $request['headers'];
			$data     = $request['data'];
			$options  = $request['options'];
			$response = self::parse_response($response, $url, $headers, $data, $options);
		} catch (Exception $e) {
			$response = $e;
		}
	}

	/**
	 * Decoded a chunked body as per RFC 2616
	 *
	 * @link https://tools.ietf.org/html/rfc2616#section-3.6.1
	 * @param string $data Chunked body
	 * @return string Decoded body
	 */
	protected static function decode_chunked($data) {
		if (!preg_match('/^([0-9a-f]+)(?:;(?:[\w-]*)(?:=(?:(?:[\w-]*)*|"(?:[^\r\n])*"))?)*\r\n/i', trim($data))) {
			return $data;
		}

		$decoded = '';
		$encoded = $data;

		while (true) {
			$is_chunked = (bool) preg_match('/^([0-9a-f]+)(?:;(?:[\w-]*)(?:=(?:(?:[\w-]*)*|"(?:[^\r\n])*"))?)*\r\n/i', $encoded, $matches);
			if (!$is_chunked) {
				// Looks like it's not chunked after all
				return $data;
			}

			$length = hexdec(trim($matches[1]));
			if ($length === 0) {
				// Ignore trailer headers
				return $decoded;
			}

			$chunk_length = strlen($matches[0]);
			$decoded     .= substr($encoded, $chunk_length, $length);
			$encoded      = substr($encoded, $chunk_length + $length + 2);

			if (trim($encoded) === '0' || empty($encoded)) {
				return $decoded;
			}
		}

		// We'll never actually get down here
		// @codeCoverageIgnoreStart
	}
	// @codeCoverageIgnoreEnd

	/**
	 * Convert a key => value array to a 'key: value' array for headers
	 *
	 * @param iterable $dictionary Dictionary of header values
	 * @return array List of headers
	 *
	 * @throws \WpOrg\Requests\Exception\InvalidArgument When the passed argument is not iterable.
	 */
	public static function flatten($dictionary) {
		if (InputValidator::is_iterable($dictionary) === false) {
			throw InvalidArgument::create(1, '$dictionary', 'iterable', gettype($dictionary));
		}

		$return = [];
		foreach ($dictionary as $key => $value) {
			$return[] = sprintf('%s: %s', $key, $value);
		}

		return $return;
	}

	/**
	 * Decompress an encoded body
	 *
	 * Implements gzip, compress and deflate. Guesses which it is by attempting
	 * to decode.
	 *
	 * @param string $data Compressed data in one of the above formats
	 * @return string Decompressed string
	 *
	 * @throws \WpOrg\Requests\Exception\InvalidArgument When the passed argument is not a string.
	 */
	public static function decompress($data) {
		if (is_string($data) === false) {
			throw InvalidArgument::create(1, '$data', 'string', gettype($data));
		}

		if (trim($data) === '') {
			// Empty body does not need further processing.
			return $data;
		}

		$marker = substr($data, 0, 2);
		if (!isset(self::$magic_compression_headers[$marker])) {
			// Not actually compressed. Probably cURL ruining this for us.
			return $data;
		}

		if (function_exists('gzdecode')) {
			$decoded = @gzdecode($data);
			if ($decoded !== false) {
				return $decoded;
			}
		}

		if (function_exists('gzinflate')) {
			$decoded = @gzinflate($data);
			if ($decoded !== false) {
				return $decoded;
			}
		}

		$decoded = self::compatible_gzinflate($data);
		if ($decoded !== false) {
			return $decoded;
		}

		if (function_exists('gzuncompress')) {
			$decoded = @gzuncompress($data);
			if ($decoded !== false) {
				return $decoded;
			}
		}

		return $data;
	}

	/**
	 * Decompression of deflated string while staying compatible with the majority of servers.
	 *
	 * Certain Servers will return deflated data with headers which PHP's gzinflate()
	 * function cannot handle out of the box. The following function has been created from
	 * various snippets on the gzinflate() PHP documentation.
	 *
	 * Warning: Magic numbers within. Due to the potential different formats that the compressed
	 * data may be returned in, some "magic offsets" are needed to ensure proper decompression
	 * takes place. For a simple progmatic way to determine the magic offset in use, see:
	 * https://core.trac.wordpress.org/ticket/18273
	 *
	 * @since 1.6.0
	 * @link https://core.trac.wordpress.org/ticket/18273
	 * @link https://www.php.net/gzinflate#70875
	 * @link https://www.php.net/gzinflate#77336
	 *
	 * @param string $gz_data String to decompress.
	 * @return string|bool False on failure.
	 *
	 * @throws \WpOrg\Requests\Exception\InvalidArgument When the passed argument is not a string.
	 */
	public static function compatible_gzinflate($gz_data) {
		if (is_string($gz_data) === false) {
			throw InvalidArgument::create(1, '$gz_data', 'string', gettype($gz_data));
		}

		if (trim($gz_data) === '') {
			return false;
		}

		// Compressed data might contain a full zlib header, if so strip it for
		// gzinflate()
		if (substr($gz_data, 0, 3) === "\x1f\x8b\x08") {
			$i   = 10;
			$flg = ord(substr($gz_data, 3, 1));
			if ($flg > 0) {
				if ($flg & 4) {
					list($xlen) = unpack('v', substr($gz_data, $i, 2));
					$i         += 2 + $xlen;
				}

				if ($flg & 8) {
					$i = strpos($gz_data, "\0", $i) + 1;
				}

				if ($flg & 16) {
					$i = strpos($gz_data, "\0", $i) + 1;
				}

				if ($flg & 2) {
					$i += 2;
				}
			}

			$decompressed = self::compatible_gzinflate(substr($gz_data, $i));
			if ($decompressed !== false) {
				return $decompressed;
			}
		}

		// If the data is Huffman Encoded, we must first strip the leading 2
		// byte Huffman marker for gzinflate()
		// The response is Huffman coded by many compressors such as
		// java.util.zip.Deflater, Ruby's Zlib::Deflate, and .NET's
		// System.IO.Compression.DeflateStream.
		//
		// See https://decompres.blogspot.com/ for a quick explanation of this
		// data type
		$huffman_encoded = false;

		// low nibble of first byte should be 0x08
		list(, $first_nibble) = unpack('h', $gz_data);

		// First 2 bytes should be divisible by 0x1F
		list(, $first_two_bytes) = unpack('n', $gz_data);

		if ($first_nibble === 0x08 && ($first_two_bytes % 0x1F) === 0) {
			$huffman_encoded = true;
		}

		if ($huffman_encoded) {
			$decompressed = @gzinflate(substr($gz_data, 2));
			if ($decompressed !== false) {
				return $decompressed;
			}
		}

		if (substr($gz_data, 0, 4) === "\x50\x4b\x03\x04") {
			// ZIP file format header
			// Offset 6: 2 bytes, General-purpose field
			// Offset 26: 2 bytes, filename length
			// Offset 28: 2 bytes, optional field length
			// Offset 30: Filename field, followed by optional field, followed
			// immediately by data
			list(, $general_purpose_flag) = unpack('v', substr($gz_data, 6, 2));

			// If the file has been compressed on the fly, 0x08 bit is set of
			// the general purpose field. We can use this to differentiate
			// between a compressed document, and a ZIP file
			$zip_compressed_on_the_fly = ((0x08 & $general_purpose_flag) === 0x08);

			if (!$zip_compressed_on_the_fly) {
				// Don't attempt to decode a compressed zip file
				return $gz_data;
			}

			// Determine the first byte of data, based on the above ZIP header
			// offsets:
			$first_file_start = array_sum(unpack('v2', substr($gz_data, 26, 4)));
			$decompressed     = @gzinflate(substr($gz_data, 30 + $first_file_start));
			if ($decompressed !== false) {
				return $decompressed;
			}

			return false;
		}

		// Finally fall back to straight gzinflate
		$decompressed = @gzinflate($gz_data);
		if ($decompressed !== false) {
			return $decompressed;
		}

		// Fallback for all above failing, not expected, but included for
		// debugging and preventing regressions and to track stats
		$decompressed = @gzinflate(substr($gz_data, 2));
		if ($decompressed !== false) {
			return $decompressed;
		}

		return false;
	}
}