A PHP internals mailing list proposal by Alex Rock outlines a two-step approach to adding a native module system to PHP. Step one introduces 'definition files' declared with `declare(def=1)` — files with zero global side effects, containing only declarations (classes, functions, constants, etc.) and no executable statements. Step two builds on this foundation to create 'PHP modules' declared with `declare(module=1)`, which gain `import` and `export` keywords for explicit, scoped dependency management. Internally, module symbols would be hash-prefixed to prevent namespace collisions, enabling tree-shaking of unused exports. The proposal also covers Composer integration via a new `spl_register_module()` function and `composer.json` fields. A proof-of-concept PR for definition files has already been submitted to php-src. A reply from Rowan Tommins raises concerns that the design mirrors JavaScript's module system too closely and may not fit PHP's Java/C#-like identity.
