I recently install OpenSUSE 11.1 using apache 2.2 and PHP5, on a server and I decide to install squirrel mail, using Yast2
By the time I was configuring it I face some problems checking on the error log files I found that this version was written in PHP4 so I decided to uninstall squirrelmail for the meantime.
Is there any new version of SquirrelMail compatible with PHP5?

Do a package search at software.opensuse.org and that will lead you to some repos with the package. It’s not in the core distro now.

You must have a very old and insecure version if it only works on PHP4.