form.php

<?php

$form = $formBuilder
    // ... add the fields
    ->add('delete', 'submit') // add delete button
    ->add('save', 'submit') // add save button
    ->getForm();

$form->handleRequest($request);

// do not check if form is valid yet
if ($form->isSubmitted()) {
    if ($form->get('delete')->isClicked) {
        // item needs to be deleted
        
        return;
    } elseif ($form->isValid()) {
        // item is valid and needs to be updated
        
        // ...
    }
}

return $this->render(/* ... render the form */);