Retrieve the underlying stream resource.
This method is called in response to stream_select().
@link http://php.net/manual/streamwrapper.stream-cast.php
int $cast_as: Can be STREAM_CAST_FOR_SELECT when stream_select() is calling stream_cast() or STREAM_CAST_AS_STREAM when stream_cast() is called for other uses.
resource|false The underlying stream resource or FALSE if stream_select() is not supported.
public function stream_cast($cast_as) {
return $this->handle ? $this->handle : FALSE;
}