Centreon is a nice, open source GUI over Nagios and allowes you to do 100% of your day to day monitoring setup and operation inside the GUI. Nice, that is, once it runs. Before that, it is a nightmare - but there is help.

The requirements page states that required PHP version is 5.3, excluding 5.3.2. Also, I am not sure if later versions of 5.3 will work. If you need some info from deeper down the rabbit hole, try

• Host, Services & Templates are not displayed after creation (config)
• When editing any object, no radio button is ever checked
• PHP 5.4 compatibility