AJAX PHP response interpretation

I noticed that there are several ways for an AJAX call made by jQuery to interpret data. I had a look at json, but maybe it is an over complication for what I am trying to do.

My php script ALWAYS returns a 1 integer string SOMETIMES followed by a 1 integer int OR a 2 integer int.

So it can either return

x or xy or xyz

where x, y, and z are real single numbers.

How could I decode this response and assign jQuery var to the reply. I was thinking something like.

var code = firstNumberOf response
var value = secondNumberOf and thirdNumberOff response

But var value can also just be the second number if there is only a second number and not a third one.

Thanks in advance, I have been dwelling on this for ages.