Gravity Forms - Button to delete file uploads for an entry

functions.php

add_filter( 'gform_entry_detail_meta_boxes', 'add_delete_attachment_meta_box', 10, 3 );
function add_delete_attachment_meta_box( $meta_boxes, $entry, $form ) {

		$my_form_id = 3;

		if ( $form['id'] == $my_form_id ) {
			if ( ! isset( $meta_boxes['payment'] ) ) {
					$meta_boxes['payment'] = array(
							'title'         => esc_html__( 'Delete Attachments', 'gravityforms' ),
							'callback'      => 'meta_box_delete_attachments',
							'context'       => 'side',
							'callback_args' => array( $entry, $form ),
					);
			}
		}
 
    return $meta_boxes;
}

function meta_box_delete_attachments( $args ) {

	$html = '<div class="wrap">';

		// Check whether the button has been pressed AND also check the nonce
		if (isset($_POST['delete_attachment_button']) && check_admin_referer('delete_attachment_button_clicked')) {
			// the button has been pressed AND we've passed the security check
			delete_these_attachments( $args );
		}

		$html .= '<form action="options-general.php?page=delete-attachment-button-slug" method="post">';
			// this is a WordPress security feature - see: https://codex.wordpress.org/WordPress_Nonces
			wp_nonce_field('delete_attachment_button_clicked');
			$html .= '<input type="hidden" value="true" name="delete_attachment_button" />';
			submit_button('Delete Attachments');
		$html .= '</form>';

		$html .= '<p style="color:red;"><strong>WARNING - Make sure you download the attachments before deleting. They will be deleted as soon as you click the button.</strong></p>';
  $html .= '</div>';


	echo $html;
}


function delete_these_attachments( $args ) {

	$form  = $args['form'];
	$entry = $args['entry'];

	$fileupload_fields = array();

	// Find all of the FileUpload fields
	foreach( $form['fields'] as $field ) {
		if ($field['type'] == 'fileupload') {
			array_push($fileupload_fields,$field['id']);
		}
	}

	$wp_dirs = wp_upload_dir();

	$delete_count = 0;

	if ( count($fileupload_fields) > 0 ) {
		foreach( $fileupload_fields as $field_id ) {
			$attachment_url = $entry[$field_id];

			$attachment_abs = str_ireplace( $wp_dirs['baseurl'], $wp_dirs['basedir'], $attachment_url );

			if ( file_exists( $attachment_abs ) ) {
				if ( unlink($attachment_abs) ) {
					$delete_count += 1;
				}
			}
		}
	}

	echo '<div id="message" class="updated fade"><p>'.$delete_count.' attachments(s) deleted.' . '</p></div>';
	?>

	<?php
}