From the "just because you can" category today Lunant has created a port of the Lisp language via an interpreter in PHP - Lisphp.

Lisphp is a Lisp dialect written in PHP. It was created to be embedded in web services or to be distributed within web applications. For that reason, it implements sandbox environment for security issues and multiple environment instances.

You can grab the latest code from the github page for the project as well as check out some of the tutorials and details about using the interpreter features like use/from, custom functions and custom macros.