PHP二分查找

function binarySearch($arr, $target) {
    $low  = 0;
    $high = count($arr) - 1;
    while($low <= $high) {
        $mid = floor(($low + $high) / 2);
        if($target == $arr[$mid]) return $mid;
        if($target > $arr[$mid])  $low  = $mid + 1;
        if($target < $arr[$mid])  $high = $mid - 1;
    }
    return false;
}
var_dump(binarySearch($arr, 4));