delete_metadata()

删除指定对象的元数据。

原型

delete_metadata( string $meta_type, int $object_id, string $meta_key, mixed $meta_value = '', bool $delete_all = false )

参数

$meta_type (string) (Required) 对象元数据的类型用于（例如，评论，帖子，术语或用户）。

$object_id (int) (Required) 对象元数据的ID用于

$meta_key (string) (Required) 元数据键

$meta_value (mixed) (Optional)  元数据价值。如果是非标量，则必须可序列化。如果指定，则仅删除具有此值的元数据条目。否则，删除具有指定meta_key的所有条目。传递null，false`或空字符串以跳过此检查。 （为了向后兼容，无法传递空字符串以删除值为空字符串的条目。）

$delete_all (bool) (Optional)   如果为true，则删除所有对象的匹配元数据条目，忽略指定的object_id。否则，仅删除指定object_id的匹配元数据条目。

返回值

(bool)  成功删除时为True，失败时为false。

源文件

路径：wp-includes/meta.php

<?php
...
function delete_metadata($meta_type, $object_id, $meta_key, $meta_value = '', $delete_all = false) {
	global $wpdb;
	if ( ! $meta_type || ! $meta_key || ! is_numeric( $object_id ) && ! $delete_all ) {
		return false;
	}
	$object_id = absint( $object_id );
	if ( ! $object_id && ! $delete_all ) {
		return false;
	}
	$table = _get_meta_table( $meta_type );
	if ( ! $table ) {
		return false;
	}
	$type_column = sanitize_key($meta_type . '_id');
	$id_column = 'user' == $meta_type ? 'umeta_id' : 'meta_id';
	// expected_slashed ($meta_key)
	$meta_key = wp_unslash($meta_key);
	$meta_value = wp_unslash($meta_value);
	/**
	 * Filters whether to delete metadata of a specific type.
	 *
	 * The dynamic portion of the hook, `$meta_type`, refers to the meta
	 * object type (comment, post, term, or user). Returning a non-null value
	 * will effectively short-circuit the function.
	 *
	 * @since 3.1.0
	 *
	 * @param null|bool $delete     Whether to allow metadata deletion of the given type.
	 * @param int       $object_id  Object ID.
	 * @param string    $meta_key   Meta key.
	 * @param mixed     $meta_value Meta value. Must be serializable if non-scalar.
	 * @param bool      $delete_all Whether to delete the matching metadata entries
	 *                              for all objects, ignoring the specified $object_id.
	 *                              Default false.
	 */
	$check = apply_filters( "delete_{$meta_type}_metadata", null, $object_id, $meta_key, $meta_value, $delete_all );
	if ( null !== $check )
		return (bool) $check;
	$_meta_value = $meta_value;
	$meta_value = maybe_serialize( $meta_value );
	$query = $wpdb->prepare( "SELECT $id_column FROM $table WHERE meta_key = %s", $meta_key );
	if ( !$delete_all )
		$query .= $wpdb->prepare(" AND $type_column = %d", $object_id );
	if ( '' !== $meta_value && null !== $meta_value && false !== $meta_value )
		$query .= $wpdb->prepare(" AND meta_value = %s", $meta_value );
	$meta_ids = $wpdb->get_col( $query );
	if ( !count( $meta_ids ) )
		return false;
	if ( $delete_all ) {
		if ( '' !== $meta_value && null !== $meta_value && false !== $meta_value ) {
			$object_ids = $wpdb->get_col( $wpdb->prepare( "SELECT $type_column FROM $table WHERE meta_key = %s AND meta_value = %s", $meta_key, $meta_value ) );
		} else {
			$object_ids = $wpdb->get_col( $wpdb->prepare( "SELECT $type_column FROM $table WHERE meta_key = %s", $meta_key ) );
		}
	}
	/**
	 * Fires immediately before deleting metadata of a specific type.
	 *
	 * The dynamic portion of the hook, `$meta_type`, refers to the meta
	 * object type (comment, post, term, or user).
	 *
	 * @since 3.1.0
	 *
	 * @param array  $meta_ids   An array of metadata entry IDs to delete.
	 * @param int    $object_id  Object ID.
	 * @param string $meta_key   Meta key.
	 * @param mixed  $meta_value Meta value.
	 */
	do_action( "delete_{$meta_type}_meta", $meta_ids, $object_id, $meta_key, $_meta_value );
	// Old-style action.
	if ( 'post' == $meta_type ) {
		/**
		 * Fires immediately before deleting metadata for a post.
		 *
		 * @since 2.9.0
		 *
		 * @param array $meta_ids An array of post metadata entry IDs to delete.
		 */
		do_action( 'delete_postmeta', $meta_ids );
	}
	$query = "DELETE FROM $table WHERE $id_column IN( " . implode( ',', $meta_ids ) . " )";
	$count = $wpdb->query($query);
	if ( !$count )
		return false;
	if ( $delete_all ) {
		foreach ( (array) $object_ids as $o_id ) {
			wp_cache_delete($o_id, $meta_type . '_meta');
		}
	} else {
		wp_cache_delete($object_id, $meta_type . '_meta');
	}
	/**
	 * Fires immediately after deleting metadata of a specific type.
	 *
	 * The dynamic portion of the hook name, `$meta_type`, refers to the meta
	 * object type (comment, post, term, or user).
	 *
	 * @since 2.9.0
	 *
	 * @param array  $meta_ids   An array of deleted metadata entry IDs.
	 * @param int    $object_id  Object ID.
	 * @param string $meta_key   Meta key.
	 * @param mixed  $meta_value Meta value.
	 */
	do_action( "deleted_{$meta_type}_meta", $meta_ids, $object_id, $meta_key, $_meta_value );
	// Old-style action.
	if ( 'post' == $meta_type ) {
		/**
		 * Fires immediately after deleting metadata for a post.
		 *
		 * @since 2.9.0
		 *
		 * @param array $meta_ids An array of deleted post metadata entry IDs.
		 */
		do_action( 'deleted_postmeta', $meta_ids );
	}
	return true;
}
...
?>

其他

英文文档：https://developer.wordpress.org/reference/functions/delete_metadata/