A pre-RFC discussion on the PHP internals mailing list proposes a new namespace load event mechanism: a callback registered via something like `spl_namespace_register($callback, $prepend)` that fires the first time PHP encounters a namespace declaration. This would enable functions and constants within a namespace to be declared before they are called, potentially solving the function autoloading problem without requiring one file per function. The thread explores design questions including callback invocation order for nested namespaces, interaction with `use` statements (which are compile-time expansions with no runtime effect), where exactly the handler should fire (on namespace declaration, before class autoloading, and before undefined function/constant errors for qualified names), and caching concerns to avoid duplicate calls. Participants draw comparisons to Python's `__init__.py` module initialization pattern.
