I just started using Aptana Studio. The first thing I did was import my php from svn repository and install the PDT tools. But whenever I open the php file, it always displays following message.

I had the PHP perspective open when I tried opening the file. Also I checked the Content Types and File Associations, where PHP Content Type has *.php listed and *.php had the PHP Editor associated with it in the file associations.
I even tried creating a new PHP project, then creating a new PHP file – couldn’t even do that – nothing showed up.
What am I missing over here?
Regards
If you are using PDT (php development toolkit), then that is your problem. PDT overrides your ‘file association’ settings and ignores your default. If you open any other perspective and open the php file, it should open to what your default is, however, you can right-click on the file and choose ‘Open With’ -> ‘PHP Source Editor’ and it will open the Aptana Studio PHP editor.
Daniel