使用memcache，redis抛出异常：连接时读取错误

In my project, I want to use redis while using memcached(It's an old system and I donnot want to outright replace memcached).But when I try to push element into a list in redis, I meet exception "read error on connection". I find if connecting memcached before connecting redis, it always throw this exception, but connecting redis firstly can avoid this problem.

ENVIRONMENT: Nginx + php-fpm + PHP 5.3.3 + Redis 2.8.19

Use connect instead of pconnect can fix this exception. But I perfer to use pconnect. Here is my code:

$memCache = new Memcached ('client');
$memCache->addServer('127.0.0.1', '8022');

$memCache->set ('mcKey', 1);
echo $memCache->get('mcKey');

$redis = new Redis();
$redis->pconnect('127.0.0.1', '6379', 1000);
$redis->setOption(Redis::OPT_READ_TIMEOUT, -1);

try {
    $redis->lPush('mykey', 1, 2);
    echo 'OK';
} catch (Exception $e) {
    echo $e->getMessage();
}

Any problem of the code here?