Selecting class using strings

I want to write an extension system for my CMS. I want the extensions to be installed by copying a folder into the extensions folder. The content of the extension is a class with the same name as the name of the folder. So my CM开发者_如何学GoS can list the extensions by the names of the folders in the extension folder. The problem is that I can't find a way to select the class even though I have a string containing it's name.

So to sum up, is there any way to create an instance of a class or calling static functions of a class, by referring to said class using a string with the class name?

I hope you understand what I mean and thanks for any help

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You mean like so?

$classname = "myClass";

$object = new $classname();