Troels Knak-Nielsen has posted a script that he's developed (for use in Emacs) to look through a PHP file and pull out all of the classes and functions found inside.

As you probably know, PHP has a ridiculous amount of functions for all kinds of things, and as it happens, token_get_all gives access to the Zend Engine tokenizer. In other words, the same chunk of code, which PHP itself uses, when reading a .php file. This provides an excellent base for writing a script, which can parse the socks off ctags.

The emacs file to bind the editor and the PHP script together is also included, making it as simple to use as binding the function key of your choice to the "php-tokens" script.