What PHP's variable variables really mean

OK, here's the thing: this is only the entrance of the rabbit hole.

If you understand what this expression really does, you realize that you're gazing upon the entrance to R'lyeh.

Do you think you don't need your soul anymore? If you do, follow me into the lair of the Elder Gods. But be warned, you will die a lot inside.

Source.

Most PHP programmers won't understand the significance of this, even after they read it. The PHP fans will even rejoice at the "flexibility" of their champion. But the purists and the weenies (and especially the smug weenies) will cringe and possibly weep at this chicanery.