About syntax: Classes, associative arrays, functions and so on...

I can not understand the example below. Can someone explain by words what is going on in this example - step by step. This is function part od classes from PHPlib session.inc: function delete() { $this->that->ac_delete($this->id, $this->name); $this->put_id(); } As my knowledge isn't great, I can see that "$this" is variable? "ac_delete()" and "put_id()" are functions? What does "that","id" and "name" mean? So, I can see actors, scene, but I can not see movie at all.... :-) For what I can use "class" in PHP? How to use associative arrays - I need some examlpe? Maybe this is not the best example, but please give me some references, or subjects that I need to read, because I can not understand sources like this one. Thanks in advance, Vladimir