private function transformChunk(string $chunk)
    {
        if (null === $this->chunkTransformer) {
            return $chunk;
        }

        return \call_user_func($this->chunkTransformer, $chunk);
    }
private function transformChunk(string $chunk)
    {
        if (null === $this->chunkTransformer) {
            return $chunk;
        }

        return \call_user_func($this->chunkTransformer, $chunk);
    }
private function transformChunk ( string $ chunk ) { if ( null === $ this -> chunkTransformer ) { return $ chunk ; } return \ call_user_func ( $ this -> chunkTransformer , $ chunk ) ; }
Transform stream chunks if required.

@param string $chunk

@return mixed The raw chunk or the transformed chunk
Transform stream chunks if required .