Include this extension in the PHP core and provide a hook API

I want to suggest to include this extension into the core to provide an API for miscellaneous userland extensions. Main idea is to give a userland code control over the produced source-code.

Chain is following: Source Code => Tokenizer => AST => Engine hooks+PHP userland hooks => Compiler => Opcodes => Execution

Why it can be a great thing: native source-code AST (static analyzers, code beautifiers), language extensions (AOP, DbC, SQL-like native syntax).

This requires to create an userland-function, probably, register_parser_extension(ParserExtensionInterface $extension) that will add an extension as parser hook.

Next additional thing is ParserExtensionInterface interface with process(Node $node) method that will receive ast\Node class and should return a modified node or tree.

Each registered extension will be called consequently, allowing to transform the source code. Last result will be used by compiler to generate final version of opcodes.

Review the proposed register_parser_extension function and ParserExtensionInterface with its process(Node $node) method, then trace the Source Code → Tokenizer → AST → Engine hooks → Compiler flow described in the issue. Define the PHP-core integration and hook behavior before implementation; done means a settled API and userland extensions can transform AST nodes before opcode generation.