ACF Phone Number Validation for Custom Post Type in WordPress

functions.php

<?php

/**
 * Validates the 'sjd_unit_phone' field for the 'sjd_orders' custom post type.
 * 
 * If the phone number format is incorrect, it prevents the post from being saved,
 * sets the post status to 'draft', and redirects the user back to the post editor 
 * with a custom query parameter to indicate validation failure.
 *
 * @param int $post_id The ID of the post being saved.
 * @return int $post_id The ID of the post being saved.
 */
function sjd_validate_sjd_unit_phone_on_save($post_id) {

	// Check for the post type.
	if (get_post_type($post_id) !== 'sjd_orders') 
		return $post_id;

	// If this is just a revision or auto save, don't send back.
	if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE) 
		return $post_id;

	// If the value of our custom field isn't set, return.
	if (!isset($_POST['acf']['field_64656c30bb9d8'])) 
		return $post_id;

	$phone = $_POST['acf']['field_64656c30bb9d8'];

	// Check if phone format is incorrect.
	if (!empty($phone) && !preg_match('/^(\(\d{3}\) \d{3}-\d{4})?$/', $phone)) {

		// Remove this action to prevent an infinite loop.
		remove_action('save_post', 'sjd_validate_sjd_unit_phone_on_save');

		// Don't save the post.
		wp_update_post(array('ID' => $post_id, 'post_status' => 'draft'));

		// Redirect back to the edit page with a custom query var.
		$location = add_query_arg('phone_validation_failed', '1', get_edit_post_link($post_id, ''));
		wp_redirect($location);
		exit;
	}

	return $post_id;
}
add_action('save_post', 'sjd_validate_sjd_unit_phone_on_save');

/**
 * Displays a notice in the admin area if phone validation has failed.
 * 
 * This function checks for the 'phone_validation_failed' query parameter 
 * and, if set, displays an error message to the user. This notice is only shown
 * when editing the 'sjd_orders' custom post type.
 */
function sjd_display_phone_validation_notice() {
	global $post_type;

	// Only show the notice for the 'sjd_orders' post type.
	if ($post_type === 'sjd_orders' && isset($_GET['phone_validation_failed']) && $_GET['phone_validation_failed'] == '1') {
		echo '<div class="notice notice-error"><p>Please use the phone format (XXX) XXX-XXXX for the unit phone field.</p></div>';
	}
}
add_action('admin_notices', 'sjd_display_phone_validation_notice');