There's nothing wrong with PHP 5. As long as he's learning about all the latest stuff, it's a perfect language. It features functional aspects to get him started and then he can graduate to OOP concepts. Since he's learning from scratch, stuff like objects and public/protected/private members might be a little farther down the line. PHP lets you get the basics of variables, arrays, functions, etc. out of the way without having to switch languages or set up some construct you have to ignore until later, when you're more adept at the language.
