链接的时候需要赋值给变量

注意这个代码的坑，非常的坑
php代码如下：

$connectionSettings = new ConnectionSettings();
$abc=$connectionSettings
->setUsername(‘test1’)
->setPassword(‘123456’)
->setKeepAliveInterval(60);

    $mqtt = new MqttClient($this->config['server'], $this->config['port'], $clientId);
    $mqtt->connect($abc, $this->config['clean_session']);
    $mqtt->publish($topic, json_encode($payload), $qos, $retain);
    $mqtt->disconnect();