redis 实现悲观锁。
原理，进去则抢锁，抢失败了 等一秒再抢，再等一秒再抢，如此反复循环。
解锁就是删掉对应的键。
/** * 实现redis 悲观锁 * User: babytuo */Class RedisLock { ???public $expire = 2; ???public function test(){ ????????$this->lock("test1"); ????????echo "111"; ???} ???public function lock($key){ ???????$redis = self::createRedisObj(); ???????$now = time(); ???????/** ?理解setnx ???????若给定的 key 已经存在，则 SETNX 不做任何动作。 ???????SETNX 是『SET if Not eXists』(如果不存在，则 SET)的简写。 ????????*/ ???????//抢锁. ???????$isLock = $redis->setnx($key , time() + $this->expire); ?//设为过期时间. ???????//不成功 ???????while ( ! $isLock) { ???????????$now++; ???????????$time = $now + $this->expire; ???????????//再重新创建 ???????????$lock = $redis->setnx($key, $time); ???????????if ($lock == 1 || ($now > $redis->get($key) && $now > $redis->getset($key, $time))) {//争锁成功后，设置新的过期时间. ???????????????break; ???????????} else { ???????????????sleep(1);//0.5s ???????????} ???????} ???????return true; ???} ???/** ????* 解锁 ????* @param type $flag ????* @return boolean ????*/ ???public function unlock($key) { ???????$redis = self::createRedisObj(); ???????$redis->del($key); ???????return true; ???} ???/** ????* 检查锁是否存在 ????* @param $key ????* @return bool ????*/ ???public function checklock($key){ ???????$redis = self::createRedisObj(); ???????return $redis->exists($key); ???} ???public static $_redis; ???/** ????* 创建一个redis 对象. ????* @return Redis ????*/ ???public static function createRedisObj(){ ???????if( ! self::$_redis){ ???????????$redis = new Redis(); ???????????$info = ?Yii::app()->cache->servers[0]; ?//读取配置 ???????????$host = $info["host"]; ???????????$port = $info["port"]; ???????????$redis->connect($host,$port); ???????????$redis_db = ???Yii::app()->settings->get(‘system‘ , ‘redis_db‘); ?//设置默认库 ???????????$redis->select($redis_db); ???????????self::$_redis = $redis; ???????} ???????return self::$_redis; ???}}php ?redis 常见应用 并发锁。（悲观锁）
原文地址：https://www.cnblogs.com/babytuo/p/9001983.html