code: public static function singularize($string) {
  
      if (substr($string, -1) == 's') {
        return substr($string, 0, -1);
      } elseif (substr($string, -1) == 'i') {
        return substr($string, 0, -1) . 'us';
      } else {
        return $string;
      }
  
    }
docs: Convert a word to the singular
  
  @param string $string The string to process
  
  @return string The result