Aptana PHP Plugin [edit]

Aptana's PHP plugin transforms Aptana Studio into an integrated development environment for PHP. This support includes PHP Debugging, Code Assist on PHP functions and parameters, improved PHP syntax colorization, and a PHP outliner.

Can I make my project a PHP project even though it wasn't originally created as one?

Yes. Edit your .project file (located in the project folder) to add the following to it:

<natures>
  <nature>com.aptana.ide.editor.php.phpnature</nature>
</natures>