That won't work unless you're only using two (or fixed digit numbers if you change 100 to 10 or 1000 etc.).
E.g.
a = 12
b = 189
(12 * 100) + 189 = 1389
12 . 189 = 12189
Easy in PHP because it's a variable type language. So the . operator uses each value as a string and then appends one to the other. If that new value is used in code as a number, it converts it.
Not sure how best to do this on an Arduino since I've not really tried programming it yet. You might have to write a function that uses itoa() on each parameter to produce string values. Appends one to the other and then atoi() to convert it back to a number. Not sure if you'd run out of range on the conversion back though.