How can I force my php scripts to run php5 ?

Some hosting providers are still using php 4 as their default for scripts, but offer php5 as well. To force your scripts to all use php5, you can try adding this to a .htaccess file on your site:

AddType x-mapp-php5 .php
AddHandler x-mapp-php5 .php

This tells the server to use php5 when it sees any .php extension on a file. If it doesn't work, remove the lines from the file, and contact your hosting provider.