Reproducing script:

<?php

function f()
{
	$data = ob_get_contents();
	while(@ob_end_clean());
	ob_start('ob_gzhandler');
	
	$step = strlen($data)/2;
	echo substr($data, 0, $step);
	ob_flush();
	echo substr($data, $step);
}

register_shutdown_function('f');

ob_start();
echo '<pre>';
readfile(__FILE__);

?>

This bug has been fixed in CVS.

Snapshots of the sources are packaged every three hours; this change
will be in the next snapshot. You can grab the snapshot at
http://snaps.php.net/.
 
Thank you for the report, and for helping us make PHP better.

Sorry, this bug is not entirely fixed.

Reproducing Script:
Similar to the previous one, but with an additional ob_end_clean()

<?php

function f()
{
	$data = ob_get_contents();
	while(@ob_end_clean());
	ob_start('ob_gzhandler');
	
	$step = strlen($data)/2;
	echo substr($data, 0, $step);
	ob_flush();
	echo substr($data, $step);
}

register_shutdown_function('f');

while(@ob_end_clean());

ob_start();
echo '<pre>';
readfile(__FILE__);

?>

==9165== Conditional jump or move depends on uninitialised value(s)
==9165==    at 0x8139541: _zval_dtor_func (zend_variables.c:35)
==9165==    by 0x812EAF1: _zval_dtor (zend_variables.h:35)
==9165==    by 0x812ECA4: _zval_ptr_dtor (zend_execute_API.c:386)
==9165==    by 0x810A41C: php_end_ob_buffer (output.c:309)

Ilia, it didn't quite do it..

This bug has been fixed in CVS.

Snapshots of the sources are packaged every three hours; this change
will be in the next snapshot. You can grab the snapshot at
http://snaps.php.net/.
 
Thank you for the report, and for helping us make PHP better.