Came across an interesting little issue this afternoon while debugging an issue with a very old osCommerce installation. This particular site uses an on the fly product thumb generator (product_thumb.php) which worked fine with PHP 5.3 but failed with PHP 5.4.
After a bit of digging I tracked the issue to this line in the original code:
imagejpeg($src, '', 100);
In PHP 5.4 this fails, and needs to be replaced with:
imagejpeg($src, NULL, 100);
Perhaps this will save someone a bit of time. I didn’t find this problem noted elsewhere.