/** * Set a regex validator for a field. The validator will check if regex is matched on form correct. * * @param Field $field The field * @param string $pattern The pattern to match. This function does not validate given pattern * @param string|null $help_text Optionally set placeholder text for field i.e. DD-MM-YYYY */ public static function validateRegularExpression(\FormHandler\Field\Field $field, $pattern, $help_text = null) { $field->setExtra(' pattern="' . $pattern . '"', true)->setValidator(function ($value) use($pattern) { return is_string($value) && preg_match($pattern, $value); }); if (!is_null($help_text)) { $field->setExtra(' placeholder="' . $help_text . '"', true); } }