If you have a host like Knownhost who is fast and knows what needs to be done, you do not have to worry much. Note: I am now worrying on which PHP script required an increase in memory allocation.

Learn how to troubleshoot Apache 2 when it's not executing PHP files with this easy-to-follow, step-by-step tutorial.

Here's a quick tutorial on how to setup Nginx with PHP support. The key? The installation of fastCGI, aka PHP-FPM, so Nginx can serve PHP files to clients.

If you're building NGINX sites, you'll probably need PHP-FPM support enabled. Jack Wallen shows you how.

How Do I Downgrade PHP?. If you'd like to downgrade your PHP installation you can do so without interfering with the path to your installation and can simply overwrite older files.