用二分查找法实现array_search

function array_search($a,$v)
{
	$b = 0;
	$n = count($a) -1;

	while($b <= $n)
	{
		$s = floor(($b + $n)/2);

		if($v == $a[$s]) return $s;

		if($v > $a[$s])
		{
			$b = $s + 1;
			continue;
		}
		else
		{
			$n = $s - 1;
			continue;
		}

		return -1;
	}
}