Debugging a PHP application can involve quite a bit of machinery, and effort getting that machinery setup. But it's worth it because what alternative is there? echo? Come on!
First get Xdebug setup
Xdebug is the project for debugging PHP. The wizard will show you how to upgrade your package version. In my case, the Xdebug packaged for Ubuntu was 2.2.3, but the more recent version is 2.3.3
Summary
Xdebug installed: 2.2.3 Server API: Apache 2.0 Handler Windows: no Zend Server: no PHP Version: 5.5.9-1 Zend API nr: 220121212 PHP API nr: 20121212 Debug Build: no Thread Safe Build: no Configuration File Path: /etc/php5/apache2 Configuration File: /etc/php5/apache2/php.ini Extensions directory: /usr/lib/php5/20121212+lfs
Caveat: their script can't really tell where the xdebug configuration lives. In Ubuntu, there is a /etc/php5/conf.d and configuration files in there add to the main php.ini. So, you end up editing sudo vim /etc/php5/conf.d/xdebug.ini
Following the sage advice of the Netbeans wiki, you want to get xdebug's debugclient working on localhost first, then add Netbeans.