"we have to indicate to the function that a parameter should be handled as an array, instead of a single number. For this, the parameter name in the function definition is prefixed by a "&"."

So the manual says that this "&" is not possible / needed with vars.. And thats absolutly wrong And it is also wrong that the "&" is only needed to "say" the function that the parameter will be an array.. this is only the most simplest explanation ^^