WordPress函数：update_metadata 更新指定对象的属性值

函数原型：

update_metadata( string $meta_type, int $object_id, string $meta_key, mixed $meta_value, mixed $prev_value = '' ): int|bool

更新指定对象的附加属性数据。如果指定的对象ID和元数据键不存在任何值，则会添加附加属性数据。

参数说明：

$meta_type，对象的类型。接受'post'、'comment'、'term'、'user'或任何其他具有关联元表的对象类型。

$object_id，对象ID。

$meta_key，属性名称。

$meta_value，属性值

$prev_value，更新前要检查的上一个值。如果指定，则仅使用此值更新现有元数据条目。否则，请更新所有条目。默认值：“”

如果具有给定键的字段不存在，因此添加了新的元字段ID，则更新成功时为true，失败时为false，或者传递给函数的值与数据库中已存在的值相同。

函数源码：

function update_metadata( $meta_type, $object_id, $meta_key, $meta_value, $prev_value = '' ) {
	global $wpdb;

	if ( ! $meta_type || ! $meta_key || ! is_numeric( $object_id ) ) {
		return false;
	}

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

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

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

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

	// expected_slashed ($meta_key)
	$raw_meta_key = $meta_key;
	$meta_key     = wp_unslash( $meta_key );
	$passed_value = $meta_value;
	$meta_value   = wp_unslash( $meta_value );
	$meta_value   = sanitize_meta( $meta_key, $meta_value, $meta_type, $meta_subtype );

	$check = apply_filters( "update_{$meta_type}_metadata", null, $object_id, $meta_key, $meta_value, $prev_value );
	if ( null !== $check ) {
		return (bool) $check;
	}

	// Compare existing value to new value if no prev value given and the key exists only once.
	if ( empty( $prev_value ) ) {
		$old_value = get_metadata_raw( $meta_type, $object_id, $meta_key );
		if ( is_countable( $old_value ) && count( $old_value ) === 1 ) {
			if ( $old_value[0] === $meta_value ) {
				return false;
			}
		}
	}

	$meta_ids = $wpdb->get_col( $wpdb->prepare( "SELECT $id_column FROM $table WHERE meta_key = %s AND $column = %d", $meta_key, $object_id ) );
	if ( empty( $meta_ids ) ) {
		return add_metadata( $meta_type, $object_id, $raw_meta_key, $passed_value );
	}

	$_meta_value = $meta_value;
	$meta_value  = maybe_serialize( $meta_value );

	$data  = compact( 'meta_value' );
	$where = array(
		$column    => $object_id,
		'meta_key' => $meta_key,
	);

	if ( ! empty( $prev_value ) ) {
		$prev_value          = maybe_serialize( $prev_value );
		$where['meta_value'] = $prev_value;
	}

	foreach ( $meta_ids as $meta_id ) {
		do_action( "update_{$meta_type}_meta", $meta_id, $object_id, $meta_key, $_meta_value );

		if ( 'post' === $meta_type ) {
			do_action( 'update_postmeta', $meta_id, $object_id, $meta_key, $meta_value );
		}
	}

	$result = $wpdb->update( $table, $data, $where );
	if ( ! $result ) {
		return false;
	}

	wp_cache_delete( $object_id, $meta_type . '_meta' );

	foreach ( $meta_ids as $meta_id ) {
		do_action( "updated_{$meta_type}_meta", $meta_id, $object_id, $meta_key, $_meta_value );

		if ( 'post' === $meta_type ) {
			do_action( 'updated_postmeta', $meta_id, $object_id, $meta_key, $meta_value );
		}
	}

	return true;
}

包含钩子：

do_action( 'updated_postmeta', int $meta_id, int $object_id, string $meta_key, mixed $meta_value )

do_action( "updated_{$meta_type}_meta", int $meta_id, int $object_id, string $meta_key, mixed $_meta_value )

do_action( 'update_postmeta', int $meta_id, int $object_id, string $meta_key, mixed $meta_value )

do_action( "update_{$meta_type}_meta", int $meta_id, int $object_id, string $meta_key, mixed $_meta_value )

apply_filters( "update_{$meta_type}_metadata", null|bool $check, int $object_id, string $meta_key, mixed $meta_value, mixed $prev_value )