In Wordpress admin media library page (upload.php) I'd like to do some checking on delete_attachment action.

I want my custom function to fire before attachment's being deleted.

In this function I want to check for it's relations with another objects in database. And delete it only if there are no relations at all.

I use this code (in functions.php) to see if my function is fired on delete_attachment:

<code>
      add_action( 'delete_attachment', 'check_relations' );
      function check_relations( $post_id ){
      ?>    
          <script>
             function myFunction() {
                 alert("Hello! I am an alert box!");
              }
      </script>
      <?php
      }

</code>

but it seems that my function's not firing at all. And image attachment is being completely deleted. What's wrong in this code?

In Wordpress admin media library page (upload.php) I'd like to do some checking on delete_attachment action.

I want my custom function to fire before attachment's being deleted.

In this function I want to check for it's relations with another objects in database. And delete it only if there are no relations at all.

I use this code (in functions.php) to see if my function is fired on delete_attachment:

add_action( 'delete_attachment', 'check_relations' );
function check_relations( $post_id ){
    ?>  
    <script>
        function myFunction() {
            alert("Hello! I am an alert box!");
        }
    </script>
    <?php
}

but it seems that my function's not firing at all. And image attachment is being completely deleted. What's wrong in this code?