用PHP实现折半（二分）查找

<?phpfunction binsearch($arr,$key){    $num = count($arr);    $left = 0;    $right = $num - 1;    while ($left <= $right) {        $mid = intval(($left + $right)/2);        if($arr[$mid] == $key){            return $mid;        }        if($arr[$mid] > $key){            //key应该在左边            $right = $mid-1;        }        if($arr[$mid] < $key){            //key应该在右边            $left = $mid+1;        }    }    return -1;}$arr = range(1,10);echo "查找7：";echo binsearch($arr,7);//$arr为升序排列的数组