original_string: public function next($t) {
          if ($t !== NULL) array_push($this->front, $t);
          return empty($this->back) ? NULL : array_pop($this->back);
      }
code: public function next($t) {
          if ($t !== NULL) array_push($this->front, $t);
          return empty($this->back) ? NULL : array_pop($this->back);
      }
code_tokens: public function next ( $ t ) { if ( $ t !== NULL ) array_push ( $ this -> front , $ t ) ; return empty ( $ this -> back ) ? NULL : array_pop ( $ this -> back ) ; }
docstring: Move hole to the next element.
  @param $t Element to fill hole with
  @return Original contents of new hole.
docstring_tokens: Move hole to the next element .