PHP is not executing scripts after Debian upgrade

Try running the following commands:

sudo apt-get purge libapache2-mod-php5

sudo apt-get install libapache2-mod-php5

sudo a2enmod php5

sudo service apache2 restart

This will reinstall all the necessary packages to get Apache capable of running mod_php.

You might also make sure that the file php5.conf is in the directory /etc/apache2/mods-enabled. If it is, you should see something like:

LoadModule php5_module /usr/lib/apache2/modules/libphp5.so

It turns out that this is a problem with one of the Apache modules. Disabling most of them resolved the problem and then we started adding them back until everything else was working.