PHP Stream Filters

You know what I want? I want to append one of those nice and shiny PHP stream filters to the output stream.

I have this nice windows-application that recives a lot of XML-data that can be compressed with a very high compression factor. And as the windows application is for people with very limited bandwith, this seems to be the perfect thing to do.

You know, I CAN compress all my output already. By doing something like this:

echo "stuff";
$c = ob_get_clean();
echo bzcompress($c);

The problem with this approach is that the data is only sent to the client once it’s assembled completely. bzip2 on the other hand is a stream compressor that is very well able to compress a stream of data and send it out as soon as a chunk is ready.

The windows client on the reciving end is certainly capable of doing that. As soon as bytes come in, it decompresses it chunk-wise and feeds it to a Expat based parser which will handle the extracted data. Now I want this to happen on the sending side aswell.

The following code does work sometimes:

  $fh = fopen('php://stdout', 'w');
  stream_filter_append($fh, 'bzip2.compress', STREAM_FILTER_WRITE, $param);
  fwrite($fh, "Stuff");

But sometimes it doesn’t and produces a incomplete bzip2-stream.

I have a certain idea of why this is happening (no sending out of data to the filter on shutdown), but I can’t prevent it. Sometimes the data is not put out which makes this method unusable.

I’m afraid to report this to as I’m sure it’s something PHP was not designed for and it’ll get marked as BOGUS faster than I can spell ‘gnegg’.

So this means that the windows-client just has to wait for the data being extracted, converted to xml and compressed.


(thinking of it, there may be this option of outputting data to a temp-file (to which handle a filter is assigned to) and the read it out to the browser immediately afterwards. But come on, this can’t be the solution, can it?)

Update: I’ve since tracked the problem to a bug in PHP itself for which I found a fix. My assumption of writing to a temporary file could help was wrong as PHP itself does not check the return value of a bzlib function correctly and never writes out a half-full buffer on stream close. Neither to the output stream nor to a file.

%d bloggers like this: