Show Alert after execute of a php script ?

Expected behavior I want my alert to show when my php code as been execute (in the IF statement)

Actual behavior It's not working ... I can only show the alert by clicking with a button...

Resources (screenshots, code snippets etc.)

HERE IS WHAT I TRIED TO MAKE BUT IT IS NOT WORKING .... :(

    <?php
    if (isset($_GET['action'])) {
      if ($_GET['action'] == 'delete') {
        foreach ($_SESSION['cart'] as $key => $value){
          if ($value['item_id'] == $_GET['id']) {
            unset($_SESSION['cart'][$key]);
            echo "<script>
            triggersBasic.forEach(function (trigger, index) {
            let instance = mdb.Alert.getInstance(document.getElementById(instancesBasic[index]));
            document.getElementById(trigger).addEventListener('click', function () {
              instance.show();
            });
            });
            </script>";
            echo "<script>$('.alert').show()</script>";
          }
        }
      }
    }
    ?>

Any help would be really appreciate ..