Why doesn't recursion work in PHP?

Question

recursion

Hello.
There is this code:

$i = 0;
 function func($arr) {
   $keys = array_keys($arr);
  echo $arr[$keys[$i]];
  $i++;
  if($i <= count($keys)){
    func($arr);
  }
}
func(['a' => 1, 'b' => 2, 'c' => 3, 'd' => 4, 'e' => 5]);

Why is there an infinite loop on one?