Aptana PHP Plugin

From Aptana

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.
There are two different ways to do so, however, we recommend the first option.

  1. Right click any project in your workspace and select 'Properties'. Select the 'Project Natures' and assign Aptana's PHP Nature to your project. Your project will be closed and reopened automatically to apply the changes.
  2. 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>

If you choose option 2, you should close&reopen your project manually to apply the changes.