DocBook XSL and Php, Chunking

Dear all,
I扉e been playing around with my XAMPP (PHP Version 5.0.5, Apache), DocBook and one of the latest XSL Snapshots. For the non-chunked version of the html output, the transformation from DB->HTML works fine. But when I try to use the xsl-based chunking, Apache crashes. 
This makes sense to me as I use a outfile file e.g. 

	$output_file = $xsltproc ->transformToXml($xml);
	file_put_contents("output/". basename($xml_file,".xml") .".htm", $output_file);

I'm no expert on php. Has someone a solution how make php's build-in xsltproc work together with xsl-based chunking?
Thanks.
Ludger Thomas