Possible to load any dll's / shared objects with PHP?

Sorry if this has been asked before but: I thought about using dll's (Windows) and shared-objects (Linux) in PHP-programs. Is there a way to: a) load such a library and b) get function-pointers to be able to call functions stored in those libs? Looking at the docs I found "dl" which seems to be restricted to php- extensions. For windows the w32api-functions (http://de2.php.net/manual/en/ref.w32api.php) seem a solution - although I hoped there was a similar interface for Linux / Windows so you just had to exchange the name of the library but leave all function-names etc. unchanged ... Regards, Stefan