I am developing with Eclipse + PDT. I've been adding phpdoc comments into my code, but actually never generated a resulting documentation in Eclipse. How should I do it - is there some functionality in Eclipse, or doc generation should be done externally?
To generate the documentation, you should use phpDocumentor, which can be installed as a PEAR package.
Then, you have to call it from command-line ; I've never seen it called from Eclipse PDT, actually.
A great solution is to have a continuous-integration platform (using phpUnderControl, for instance), and integrate to creation of the phpdoc in your build configuration file ; this way, the phpdoc is generated everytime someone commits (or once a day, or whenever you want ^^ ).
In Eclipse PDT, you can call "external tools" (see "Run > External Tools" in the menu) ; this would allow you to launch the phpdoc command (like you do from CLI) ; but it definitly is not as user-friendly as what Zend Studio offers -- not the same price either, though ^^