493 

   494 	/**

   495 	 * Get etag header for cache validation.

   496 	 *

   497 	 * @since 6.7.0

   498 	 *

   499 	 * @global string $wp_version The WordPress version string.

   500 	 *

   501 	 * @param string[] $load Array of script or style handles to load.

   502 	 * @return string Etag header.

   503 	 */

   504 	public function get_etag( $load ) {

   505 		/*

   506 		 * Note: wp_get_wp_version() is not used here, as this file can be included

   507 		 * via wp-admin/load-scripts.php or wp-admin/load-styles.php, in which case

   508 		 * wp-includes/functions.php is not loaded.

   509 		 */

   510 		global $wp_version;

   511 

   512 		$etag = "WP:{$wp_version};";

   513 

   514 		foreach ( $load as $handle ) {

   515 			if ( ! array_key_exists( $handle, $this->registered ) ) {

   516 				continue;

   517 			}

   518 

   519 			$ver   = $this->registered[ $handle ]->ver ?? $wp_version;

   520 			$etag .= "{$handle}:{$ver};";

   521 		}

   522 

   523 		/*

   524 		 * This is not intended to be cryptographically secure, just a fast way to get

   525 		 * a fixed length string based on the script versions. As this file does not

   526 		 * load the full WordPress environment, it is not possible to use the salted

   527 		 * wp_hash() function.

   528 		 */

   529 		return 'W/"' . md5( $etag ) . '"';

   530 	}