二分查找

<?php

function binsearch($n,$array){

		$start = 0;
		$end = count($array);
		$pos = false;

		do{

			$mid = (int) (($start + $end)/2);


			if($n > $array[$mid]){
				$start = $mid;
			}else if($n < $array[$mid]){
				$end = $mid;
			}else if($n===$array[$mid]){
				return $mid;
			}
			
			if($start===$mid || $end===$mid){
				return false;
			}
			
		}while(!$pos);
		
		return false;

}

$n = 6;
$array=[1,2,4,5,7,8,9,10];
echo binsearch($n,$array);