php如何在数组种找出缺失数字

function missingNumber($nums) {
  $min = 0;
  $max = count($nums) - 1;
  while ($min <= $max) {
     $mid = (int)($min + ($max - $min) / 2);
     $mid == $nums[$mid] ? $min = $mid + 1 : $max = $mid - 1;
  }
  return $min;
}