1 $arr=array(33,2,54,25,65,34,67,42,87,90,243,213,365,78,67,345,678); 2 sort($arr);//二分查找，一定要在一个有序的里面查找 3 sortAll($arr,54); 4 function sortAll($arr,$key,$low='0',$high='0'){ 5     if($high==0){ 6         $high=count($arr); 7     } 8     $mid=intval(($low+$high)/2); 9     if($arr[$mid]==$key){10         echo  $arr[$mid].'====='.$mid;11     }else if($arr[$mid]<$key){12         sortAll($arr,$key,$mid,$high);//递归实现13     }else if($arr[$mid]>$key){14         sortAll($arr,$key,$low,$mid);//递归实现15     }else{16         echo 'sorry,not found!';17     }18 }