Thanks in part to http://sachachua.com/blog/2008/07/eclipse-to-emacs-navigating-your-source-tree/
Set-up:
(If not already installed: sudo apt-get install exuberant-ctags)
sudo apt-get install exuberant-ctags
ctags -R -f ctagstags --languages=php --langmap=php:.module.php.inc.engine.profile .
In .vimrc,
set tags=ctagstags;/
In .bashrc