PhpDoc documenting comments additional support package is now available, through PackageControl or at GitHub.
Currently, it supports unwrapping function declarations into a proper phpdoc template. Documenting keywords for auto-completion are also available (though not as conveniently, as I would want them to be — the built-in php auto-completions get in the way quite a bit, and there is nothing I can do, apparently).
That’s pretty much what one’ll have on top of what is already implemented in ST2.