(PHP 5 >= 5.3.0, PHP 7)
streamWrapper::stream_cast — Retrieve the underlaying resource
$cast_as
   )This method is called in response to stream_select().
cast_as
       Can be STREAM_CAST_FOR_SELECT when
       stream_select() is calling
       stream_cast() or
       STREAM_CAST_AS_STREAM when
       stream_cast() is called for other uses.
      
   Should return the underlying stream resource used by the wrapper, or FALSE.