original_string: public function css($string)
      {
          if (!$string) {
              return $string;
          }
  
          $string = $this->toUtf8($string);
          if ($string === '' || ctype_digit($string)) {
              return $string;
          }
  
          $result = preg_replace_callback('/[^a-z0-9]/iSu', $this->cssMatcher, $string);
          return $this->fromUtf8($result);
      }
code: public function css($string)
      {
          if (!$string) {
              return $string;
          }
  
          $string = $this->toUtf8($string);
          if ($string === '' || ctype_digit($string)) {
              return $string;
          }
  
          $result = preg_replace_callback('/[^a-z0-9]/iSu', $this->cssMatcher, $string);
          return $this->fromUtf8($result);
      }
code_tokens: public function css ( $ string ) { if ( ! $ string ) { return $ string ; } $ string = $ this -> toUtf8 ( $ string ) ; if ( $ string === '' || ctype_digit ( $ string ) ) { return $ string ; } $ result = preg_replace_callback ( '/[^a-z0-9]/iSu' , $ this -> cssMatcher , $ string ) ; return $ this -> fromUtf8 ( $ result ) ; }
docstring: Escape a string for the CSS context. CSS escaping can be applied to any string being
  inserted into CSS and escapes everything except alphanumerics.
  
  @param string $string
  @return string
docstring_tokens: Escape a string for the CSS context . CSS escaping can be applied to any string being inserted into CSS and escapes everything except alphanumerics .