My server is configurated using this howto: http://www.howtoforge.com/perfect-server-centos-5.5-x86_64-ispconfig-3 For another project I need php 5.3 and I tried to install it using this howto: http://www.howtoforge.com/centos-5.6-php53-common-conflicts-with-php-common Centos is updated to version 5.8 Final. Installing php 5.3 was no problem an checking with php -v gave me version 5.3.10. The problem was that afterwards users from my site couldn't log in to the memberpages. I made a testpage with this code: PHP: <?php session_start(); if(isset($_SESSION['views'])) $_SESSION['views']=$_SESSION['views']+1; else $_SESSION['views']=1; echo "Views=". $_SESSION['views']; ?> and refreshing this page the number didn't change. So I concluded that sessions didn't function. Downgrading to php 5.1.6 and everything worked again. The testpage also counted after refreshing. I really would like to use php 5.3 Do I also have to change Apache and Mysql versions, or do I have to change something in the php.ini files? Who knows a solution? Ad.