Edit file File name : classes-prop-type.php Content :<?php namespace Elementor\Modules\AtomicWidgets\PropTypes; if ( ! defined( 'ABSPATH' ) ) { exit; // Exit if accessed directly. } class Classes_Prop_Type extends Transformable_Prop_Type { public static function get_key(): string { return 'classes'; } protected function validate_value( $value ): void { if ( ! is_array( $value ) ) { throw new \Exception( 'Value must be an array, ' . gettype( $value ) . ' given.' ); } if ( ! $this->all_are_valid_classes( $value ) ) { throw new \Exception( 'All classes must start with an english letter, and contain only english letters, numbers, hyphens, and underscores.' ); } } private function all_are_valid_classes( array $values ) { return array_reduce( $values, function ( $carry, $item ) { return $carry && is_string( $item ) && preg_match( '/^[a-z][a-z-_0-9]*$/i', $item ); }, true ); } } Save