original_string: public function getCacheFile($id)
      {
          assert('is_string($id)');
  
          $cacheFile = strval($this->cacheDirectory).'/'.$id;
          if (!file_exists($cacheFile)) {
              return null;
          }
  
          return $cacheFile;
      }
code: public function getCacheFile($id)
      {
          assert('is_string($id)');
  
          $cacheFile = strval($this->cacheDirectory).'/'.$id;
          if (!file_exists($cacheFile)) {
              return null;
          }
  
          return $cacheFile;
      }
code_tokens: public function getCacheFile ( $ id ) { assert ( 'is_string($id)' ) ; $ cacheFile = strval ( $ this -> cacheDirectory ) . '/' . $ id ; if ( ! file_exists ( $ cacheFile ) ) { return null ; } return $ cacheFile ; }
docstring: Get the cache filename for the specific id.
  
  @param string $id  The identifier of the cached data.
  @return string|null  The filename, or NULL if the cache file doesn't exist.
docstring_tokens: Get the cache filename for the specific id .