A scripting language is no less powerful than a compiled language – at least in theory. Compiled languages can, however, be substantially faster. And generally speaking, the kind of low-level coding done when building an operating system is limited to compiled languages. But that doesn’t mean that scripting languages are not powerful. PHP is a complete programming language. From the standpoint of building web applications, you can do pretty much anything you need with it. And using a more “powerful” language like C++ for creating a web page would be a terrible idea because it is powerful in a way that isn’t consistent with the needs of that effort.