前提：查询数组是一个有序数组
算法思想：取middle=(low+high)/2索引的元素值，比较arr[middle]与result， 若查找值result<arr[middle],对low~middle-1进行如上查找，若result>arr[middle],对middle+1~high进行如上查找，如此循环递归，一直到查得或low>high;
代码：
<?php $arr = array(3,12,44,45,54,232,234,289,322,323,456,554,2323,3432,3435,34454,43546); function binarySearch(&$arr, $low, $high, $result) { if($low>$high) return "No such digit!"; $middle = round(($low+$high)/2); if($arr[$middle] == $result) return $middle; else if($result <$arr[$middle]) return binarySearch($arr, $low, $middle-1, $result); else return binarySearch($arr, $middle+1, $high, $result); } echo binarySearch($arr, 0, count($arr)-1, 44); ?>
原文：http://www.cnblogs.com/fantasy01/p/4154101.html