In this last years a lot of high traffic web sites have been built in PHP. One of the main problem to design a distributed PHP architecture is how to share session data between multiple servers. In this presentation we showed the most used solutions to scale a PHP application along multiple servers. We presented different solutions to share session data using open source solutions (nfs, databases, memcached, redis, etc). Moreover we talk about Zend Server Cluster Manager, an enterprise ready Web Application Server for running and managing an HA Cluster of PHP servers.