Assuming you' re familiar with the concept of functions (if you're not, take a look at the chapter about functions), you'd assume that typing $c = foo() is essentially just like writing $c = 5, and you're right.
Če predvidevamo, da ste seznanjeni s konceptom funkcij (če niste, si oglejte poglavje o funkcijah), bi predvidevali da ko zapišete $c = foo(), je to pravzaprav enako, kot če bi zapisali $c = 5 - kar je popolnoma pravilno.