Proper way to remove an element from an array

I know in some languages there's a right way to remove an element from an array and other ways that will give you problems. In PHP can I just set $arrayname[key] = null? Or will I then end up with key => null as a value. I looked on php.net under array functions for a bit and I didn't find any sort of remove element function. I've just never needed to do this before. - Dan