$ip = $_SERVER['REMOTE_ADDR'];
$content = file_get_contents(‘http://ip.taobao.com/service/getIpInfo.php?ip='.$ip);
$banned = json_decode(trim($content), true);
$lan = strtolower($_SERVER['HTTP_ACCEPT_LANGUAGE']);
if((!empty($banned['data']['country_id']) && $banned['data']['country_id'] == ‘CN') || strstr($lan, ‘zh'))
{
header(“HTTP/1.0 404 Not Found”);
echo ‘HTTP/1.0 404 Not Found';
exit;
}

$redis->setnx(‘lock:hot_items', true)尝试创建一个key作为”锁”.若key已存在,setnx不会做任何动作且返回值为false,所以只有一个客户端会返回true值进入if语句更新缓存. 
$redis = new redis();
$redis_key = ‘lock:hot_items';
$clock_expire_time = $redis->get($redis_key);
if(!empty($clock_expire_time) && time() > intval($clock_expire_time))
{
//解除当前Redis锁
$redis->delete($redis_key);
}

if($redis->setnx($redis_key, time() + 3) !== true)
{
echo ‘高并发有冲突';
}

//操作你的代码, 同一时刻就一个人访问该代码了

//解除当前Redis锁
$redis->delete($redis_key);