Attach a filter to a stream
stream_filter_append ( resource $stream , string $filtername [, int $read_write [, mixed $params ]] ) : resource
The target stream.
The filter name.
By default, stream_filter_append() will attach the filter to the read filter chain if the file was opened for reading (i.e. File Mode: r, and/or +). The filter will also be attached to the write filter chain if the file was opened for writing (i.e. File Mode: w, a, and/or +). STREAM_FILTER_READ, STREAM_FILTER_WRITE, and/or STREAM_FILTER_ALL can also be passed to the read_write parameter to override this behavior.
This filter will be added with the specified params to the end of the list and will therefore be called last during stream operations. To add a filter to the beginning of the list, use stream_filter_prepend().
Returns a resource on success or FALSE on failure. The resource can be used to refer to this filter instance during a call to stream_filter_remove().
FALSE is returned if stream is not a resource or if filtername cannot be located.
Resource id #4