Originally Posted by cardinal&gold
I know from experience that upgrading from PHP 4 to PHP 5 alone can cause all kinds of problems, to say nothing of also upgrading Apache and MySQL. Hope the upgrade goes smoothly.
Apache 1 to Apache 2 is total cake if you are not using any of the advanced modules. Mysql 4 to 5 is pretty easy too. PHP on the other hand was a **** to get working for me.