I wanted to process the output buffer by myself first to 'tidy up' HTML/JavaScript code a bit and then use the gzip-compression for a faster transfer. I used this demo script to test this:

<?php
function my_ob_handler($x)
{
	# this normally tidies html code....
	return strtoupper($x);
}

function proc_out($x)
{
	return ob_gzhandler(my_ob_handler($x));
	#return my_ob_handler($x);
}

if (ob_get_length() === false)
{
	#ob_start("ob_gzhandler");
	ob_start("proc_out");
}
?>

abcABCabc12345

.

When I only set "ob_gzhandler" as output handler, it works and I see the text. When I use "proc_out" and don't call "ob_gzhandler" by myself, it also works. But when I want to use both handlers in queue, I get nothing at all.

My provider uses PHP 4.1.1 and I can't upgrade it! I have PHP 4.2.1 at home but with no zlib support to test this.