I am thinking about using CPP program to access data or/and PHP. Running Linux since January and still not starting to work with PHP I am

I don't think you need to play too much with non-PHP stuff as all major code is already written. As one of my experiments I did embed HTTP server itself into MediaWiki PHP framework. It was fast, though, had some of issues to solve, like too many 'exit' points. Though, for read only operations there are not too many of them. As for direction of development I'd choose as Brion advised some scripts in maintenance/, and make them export data suitable for easy embedding to your software. Or even use PHP Gtk :)

Domas