Create a new language with a monadic parser combinator written in PHP

Without $, how do you distinguish a constant from a variable?

Concise: use + and - to set static or instance methods, \ for private, | for protected, / for public

This seems more confusing. \ vs / does not scream public vs private. Seems like something I'd have to keep looking up.

Safe by default: all the calls to echo or print ar wrapped with htmlentities, to prevent XSS flaws

You should be using a templating system like Smarty, and not echoing or printing HTML output