Un tuto complet sur comment faire cohabiter PHP 5.3 et 5.2 sur un même serveur :
http://www.bsntech.com/bsntech-blog-mainmenu-321/computers-mainmenu-281/1681-install-two-versions-of-php-on-ubuntu-lucid-1004-php-53-and-php-52.html
"First they ignore you, then they laugh at you, then they fight you, then you win." [Mahatma Gandhi]