Many web production systems because of compatibility issues base on Apache2 backend and Nginx frontend servers. This solution gives a good known and configurable environment for all out of the box web products. The simplest method is installing an apache2-mpm-prefork with mod-php5 module. Unfortunately this solution has very poor performance. How to increase the performance of that system? Use CGI version of PHP and fcgi module instead of mod-php5. What you have to do on Debian?
Install apache apache2-mpm-worker and libapache2-mod-fcgid:
# apt-get install apache2-mpm-worker libapache2-mod-fcgid
# apt-get install php5-cgi
Then you can configure php5-cgi. Remember to use configuration file for cgi version!
# vim /etc/php5/cgi/php.ini
The last thing to change is a virtual host configuration. Add the following lines to the virtual host configuration file.
AddHandler fcgid-script .php FCGIWrapper /usr/lib/cgi-bin/php5 .php Options +ExecCGI
Restart Apache and test your configuration.