Sebastian Bergmann's Blog: Scalar Type Hints in PHP 5.3.99
In the theme of other recent posts mentioning the scalar type hinting that has been included in the main line of code that is headed towards the next PHP release, Sebastian Bergmann has a new post about their inclusion in PHP 5.3.99 (yes, that's PHP 5.4) and the new syntax it introduces.
In a nutshell, this means that PHP 5.3.99 introduces new syntax -- scalar type hints -- but no new semantics. The latter can either be implemented as an extension written in C/C++, in userland PHP code, or in a tool that statically analyzes the code.
He includes an example fro userland with a "php_check_parameters" function that looks at the arguments of the current method and uses Reflection to check against the type hints for the correct value type.