original_string: protected function stripExistingCssCharsets($css)
      {
          if (!($css = (string) $css)) {
              return $css; // Nothing to do.
          }
          $css        = preg_replace('/@(?:\-(?:'.$this->regex_vendor_css_prefixes.')\-)?charset(?:\s+[^;]*?)?;/ui', '', $css);
          return $css = $css ? trim($css) : $css;
      }
code: protected function stripExistingCssCharsets($css)
      {
          if (!($css = (string) $css)) {
              return $css; // Nothing to do.
          }
          $css        = preg_replace('/@(?:\-(?:'.$this->regex_vendor_css_prefixes.')\-)?charset(?:\s+[^;]*?)?;/ui', '', $css);
          return $css = $css ? trim($css) : $css;
      }
code_tokens: protected function stripExistingCssCharsets ( $ css ) { if ( ! ( $ css = ( string ) $ css ) ) { return $ css ; // Nothing to do. } $ css = preg_replace ( '/@(?:\-(?:' . $ this -> regex_vendor_css_prefixes . ')\-)?charset(?:\s+[^;]*?)?;/ui' , '' , $ css ) ; return $ css = $ css ? trim ( $ css ) : $ css ; }
docstring: Strip existing charset rules from CSS code.
  
  @since 140417 Initial release.
  
  @param string $css CSS code.
  
  @return string CSS after having stripped away existing charset rules.
docstring_tokens: Strip existing charset rules from CSS code .