microphp

A small subset of PHP implemented in Rust.

About

This project aims to implement a small subset of PHP's feature-set using a Rust powered parser and virtual machine.

It uses a recursive-descent parser based on binding power similar to PHP's own precedence model. The interpreter is a bytecode virtual machine where the AST is compiled into a series of bytecode operations and constants. The virtual machine is stack-based, whereas PHP's Zend Engine is a register-based machine.

Both engines share similar opcodes making implementation of features much simpler as the structure and flow of the program can essentially be replicated.

Supported Features

• Strings (surrounded by double-quotes)
• A handful of binary and boolean operations.
• If/else statements (no else if support)
• While statements (along with break)
• User-defined functions (no default parameter values or type declarations)
• Internal / native functions

Optimisations

• Use a Vec<Value> and store each variable against an index, instead of storing things in a HashMap.
• Intern strings to reduce memory consumption.
• Make arrays a little bit better (string keys and maintain insertion order).