GraphQL\Utils::printSafe PHP Метод

    public static function printSafe($var)
    {
        if ($var instanceof Type) {
            return $var->toString();
        }
        if (is_object($var)) {
            return 'instance of ' . get_class($var);
        }
        if (is_scalar($var)) {
            return (string) $var;
        }
        if (null === $var) {
            return 'null';
        }
        return gettype($var);
    }

 public function parseValue($value)
 {
     if (!filter_var($value, FILTER_VALIDATE_EMAIL)) {
         throw new \Exception('Cannot represent value as email: ' . Utils::printSafe($value));
     }
     return $value;
 }