A useful development environment for PHP/HTML/CSS in Ubuntu and other Linux Platform. gPHPEdit is a GNOME2 editor for editing PHP files and other supporting files, like HTML/CSS. It has support for drop-down function lists, hints showing parameters, and syntax highlighting.
Howto Install GPHPEdit in Ubuntu
Open a Terminal
$sudo apt-get install gphpedit
or use Synaptic PAckage Manager