function binarySearch($arr,$findval,$leftIndex,$rigthIndex){    if($leftIndex > $rigthIndex){       echo ‘找不到这个数‘;       return ;    }    $middleIndex = round(($leftIndex+$rigthIndex)/2);    if($findval > $arr[$middleIndex]){        binarySearch($arr, $findval, $middleIndex+1, $rigthIndex);    }else if($findval < $arr[$middleIndex]){        binarySearch($arr, $findval, $leftIndex, $middleIndex-1);    }else{        echo ‘这个数的下标是‘. $middleIndex;    }}