二分查找（while循环）

<?php
function binary($arr,$low,$high,$element)
{
while($low <= $high)
{
$mid = floor(($low+$high)/2);
if($arr[$mid] == $element)
{
return $mid;
} elseif ($arr[$mid] < $element)
{
$low = $mid + 1;
} else 
{
$high = $mid - 1;
}
}


return 'No';
}


$a = [2,4,6,8,10];
echo binary($a,0,count($a)-1,8);