无法在PHP中实例化两次相同的类

我有以下代码，我想通过传递$ redisdb param连接到2个服务器。不幸的是二审获得第一次联系。无法在PHP中实例化两次相同的类

$redis = new RedisHandler(); 
    $redis2 = new RedisHandler('redis2'); //this one gets first $redis connection

我在做什么错？

class RedisHandler 
{ 
    static $db = null; 
    public function __construct($redisdb = 'redis') { 
     // opening db connection 
     return self::connect($redisdb); 
    } 
    static public function connect($redisdb) 
    { 
     global $config; 
     if (self::$db === null) 
     { 
      try { 
       $redisClient = new Redis(); 
       $redisClient -> connect($config[$redisdb]['host'], $config[$redisdb]['port'], $config[$redisdb]['timeout'], null, $config[$redisdb]['reservedInterval']); 
       $redisClient->setOption(Redis::OPT_READ_TIMEOUT, 100); 
       if (!$redisClient) { throw new Exception("Can't connect to Redis"); } 
      } catch (Exception $e) { 
       die('Failed to connect to Redis '.$e->getMessage()); 
      } 
      self::$db = $redisClient; 
      return self::$db; 
      //return $m; 
     } 
     else 
     { 
      // return self::$db; 
      return self::$db; 
     } 
    } 
}

来源

2017-05-04 Alexandru Rada

那么，你是静态存储只有一个连接，没有太大的不同，从一个全局变量... – deceze