code: protected static function validateSyntax($json, $file = null)
      {
          $parser = new JsonParser();
          $result = $parser->lint($json);
          if (null === $result) {
              if (defined('JSON_ERROR_UTF8') && JSON_ERROR_UTF8 === json_last_error()) {
                  throw new \UnexpectedValueException('"'.$file.'" is not UTF-8, could not parse as JSON');
              }
  
              return true;
          }
  
          throw new ParsingException('"'.$file.'" does not contain valid JSON'."\n".$result->getMessage(), $result->getDetails());
      }
docs: Validates the syntax of a JSON string
  
  @param  string                    $json
  @param  string                    $file
  @throws \UnexpectedValueException
  @throws ParsingException
  @return bool                      true on success