MadLisp - Lisp ♥ PHP

MadLisp is a Lisp interpreter written in PHP by Pekka Laiho. It is inspired by the Make a Lisp project, but does not follow that convention or syntax strictly. It provides a fun platform for learning functional programming.


  • REPL environment where the user can interactively experiment with the language. Suitable for executing pieces of code one by one and examining the internal state of the system.
  • Minimal safeguards or restrictions as to what can be done. Breaking things or using the language in unexpected ways should be part of the fun.
  • Performance does not need to match commercial-grade languages, but needs to be fast enough for real-world programs and uses cases.
  • Suitable to be used as a scripting language in Linux shell scripts and similar environments.
  • Suitable to be used as an embedded scripting language inside another PHP application.
  • Clear and intuitive error messages. This is important for pleasant user experience.
  • Provide a library with commonly used features such as HTTP requests, JSON processing and SQL database support.
  • Provide a clean interface for extending the language with your own functions defined in PHP.
  • Provide a safe-mode where access to the file system and other external I/O is restricted.
  • Provide a debug mode which shows what is happening inside the code evaluation.
  • Loosely respect the Lisp legacy with things like naming conventions but do not be constrained by it.


  • Ability to call arbitrary PHP functions directly. The language should have control over which PHP functions can be called and how.
  • Namespaces or similar mechanisms. The global namespace is a feature, not a bug! Use a prefix for your function names if this becomes a problem.
  • Support for classes and object-oriented programming.


The project requires PHP 7.4 or newer and Composer.


The repository is hosted on GitHub.


MadLisp is licensed under the MIT license.