wp_media_attach_action( int $parent_id, string $action = 'attach' )

Source

File: wp-admin/includes/media.php

function wp_media_attach_action( $parent_id, $action = 'attach' ) {
	global $wpdb;

	if ( ! $parent_id ) {
		return;
	}

	if ( ! current_user_can( 'edit_post', $parent_id ) ) {
		wp_die( __( 'Sorry, you are not allowed to edit this post.' ) );
	}

	$ids = array();

	foreach ( (array) $_REQUEST['media'] as $attachment_id ) {
		$attachment_id = (int) $attachment_id;

		if ( ! current_user_can( 'edit_post', $attachment_id ) ) {
			continue;
		}

		$ids[] = $attachment_id;
	}

	if ( ! empty( $ids ) ) {
		$ids_string = implode( ',', $ids );

		if ( 'attach' === $action ) {
			$result = $wpdb->query( $wpdb->prepare( "UPDATE $wpdb->posts SET post_parent = %d WHERE post_type = 'attachment' AND ID IN ( $ids_string )", $parent_id ) );
		} else {
			$result = $wpdb->query( "UPDATE $wpdb->posts SET post_parent = 0 WHERE post_type = 'attachment' AND ID IN ( $ids_string )" );
		}
	}

	if ( isset( $result ) ) {
		foreach ( $ids as $attachment_id ) {
			/**
			 * Fires when media is attached or detached from a post.
			 *
			 * @since 5.5.0
			 *
			 * @param string $action        Attach/detach action. Accepts 'attach' or 'detach'.
			 * @param int    $attachment_id The attachment ID.
			 * @param int    $parent_id     Attachment parent ID.
			 */
			do_action( 'wp_media_attach_action', $action, $attachment_id, $parent_id );

			clean_attachment_cache( $attachment_id );
		}

		$location = 'upload.php';
		$referer  = wp_get_referer();

		if ( $referer ) {
			if ( false !== strpos( $referer, 'upload.php' ) ) {
				$location = remove_query_arg( array( 'attached', 'detach' ), $referer );
			}
		}

		$key      = 'attach' === $action ? 'attached' : 'detach';
		$location = add_query_arg( array( $key => $result ), $location );

		wp_redirect( $location );
		exit;
	}
}