Q:

Aptana launches new Aptana instance when double-clicking a PHP file

This happens until I right-click and open the file once by selecting "Open with > Text editor". Subsequent double-clicks on that PHP file will open in the same Aptana instance. Any ideas about how to fix this?

A:

Which version of Aptana Studio are you using?
In Studio 2, there is no default PHP plugin installed, so there is no PHP editor, and until you install the PDT plugin, you will get the above behavior.
In Studio 3, there is a default PHP plugin, so a double-click on a file should open it in the PHP editor.
As pointed out above, once you explicitly pick an editor for a file, it will continue to open in that editor. You can set up file associations here:
http://wiki.appcelerator.org/display/tis/Changing+your+file+association+preferences

