Apache2 does not process php as php

Question

In my Ubuntu server (12.04) with apache2, I needed php5.5 instead of php5.3. So I upgraded. I also had to apt-get install apache2-mpm-prefork because apache was asking for it.

Now php files won't run and are loaded as text. I understand that suddenly php is not processed as php and I have checked relevant questions and answers in stackoverflow but nothing seems to work for me.

Do you have any advice?

Answer 1

I solved my problem by installing php again. The particular thing that fixed the problem was to chose to use the package's php.ini settings instead of keeping the existing settings (when I previously upgraded, I kept my own settings, and this seems to have been the source of the problem)