please let me add something to this topic, because I have to spend a lot of time to find a solution for a problem.
After the update to php5 with apt-get and the parameters above apache and php5 works, but mysql and gd-support for example is per default not active.
For activation the modules it is neccessary the modify the php.ini (/etc/php5/apache2/php.ini). In the Section "Dynamic Extensions" you have to integrate the modules - for example: "extension=mysql.so".
Then restart the apache and everything works fine
I hope this will help for some "isp-config fighter" to save time ...