PHP 实现二分查找

$arr = [1, 4, 6, 8, 23, 43, 57]; //数组必须是有序的
$count = count($arr);
    function middle($arr, $find)
    {

        $len = count($arr);
        if ($len == 1) {
            return $arr[0] == $find ? 0 : -1;
        }
        $low = 0;
        $high = $len - 1;
        while ($low <= $high) {
            $mid = $low + (($high - $low) >> 1);
            if ($arr[$mid] == $find) {
                return $mid;
            } else {
                if ($arr[$mid] > $find) {
                    $high = $mid - 1;
                } else {
                    $low = $mid + 1;
            }
        }
        return -1;

    }
var_dump(middle($arr, 23)); //4
die;