code: public function quote(
          /*# string */ $string,
          /*# bool */ $quote = DialectInterface::QUOTE_YES
      )/*# : string */ {
          $pref = $this->quote_prefix;
          $suff = $this->quote_suffix;
  
          // space found
          if (preg_match("/[ \n(),]/", $string)) {
              // quote it anyway
              if ($quote & DialectInterface::QUOTE_SPACE) {
                  return sprintf('%s%s%s', $pref, $string, $suff);
  
              // abort
              } else {
                  return $string;
              }
          }
  
          if ($quote & DialectInterface::QUOTE_YES) {
              $string = preg_replace_callback(
                  '/\b([0-9a-zA-Z\$_]++)\b/',
                  function($m) use ($pref, $suff) {
                      return sprintf('%s%s%s', $pref, $m[1], $suff);
                  },
                  $string
              );
          }
          return $string;
      }
docs: {@inheritDoc}