code: protected function isOnlyAscii($ascii)
      {
          for ($i = 0, $length = strlen($ascii); $i < $length; $i++) {
              if (ord($ascii[$i]) > 127) {
                  return false;
              }
          }
  
          return true;
      }
docs: Tests each character is in the range 0-127.
  
  @param string $ascii    String to test.