How do I properly declare this as a function in Mathematica?

Question

I want to create a simple function that prints all prime numbers from 1 to x. I have the following code, which doesn't cause any errors from the kernel but it doesn't return anything:

allprimes[x_] = For[i=0, i<=x, i++, 
                     If[PrimeQ[i], Print[i]]]

What have I done wrong?