Display HTML toolbar when PHP file is opened
If you are using Eclipse IDE with Aptana 2.0 plugin and want to display HTML toolbar even when you have PHP file opened, just follow these instructions:
1. Go to Preferences -> General -> Editors -> File Associations
2. In file types choose .php extension
3. In associated editors click Add button.
4. Choose “Aptana HTML editor” from internal editors.
5. Save your changes by clicking OK
6. Now you should see HTML toolbar even when you have PHP file opened.
I hope this is just a temporal solution and Aptana developers (or PDT team) will implement this feature in future realeases of PDT plugin.

Unfortunately this did not work for me. :/
I agree with your statement that hopefully this functionality will be returned by default as in previous versions of Aptana.