二分法

<?php
    $arr=array(0,1,2,3,4,5);
    
    function chazhao2(&$arr,$search,$start,$end){
        
        
        if($start>$end){
            echo '没找到哦';
            return ;
        }
        
        $mid=round(($start+$end)/2);
        
        if($search>$arr[$mid]){
            chazhao2($arr,$search,$mid+1,$end);
        }elseif($search<$arr[$mid]){
            chazhao2($arr,$search,$start,$mid-1);
        }else{
            echo '找到了，查找的下边是：'.$mid;
        }
    };
    
    chazhao2($arr,5,0,count($arr)-1);
?>