How to fix eternal recursion?

Question

PHP

I want to make a function that every time, provided that the number is more than one hundred, will subtract 5 from it, but for some reason the browser goes into eternal recursion and simply subtracts 5, not even every time, but one-time, here is the construction itself:

function number($sum){
  if ($sum > 100) {
    echo $sum - 5;
    number($sum);
  }else return;
}
number(156);

Answer 1

The eternal recursion happens because you never change the value$sum