检查与服务器的连接是否已打开 - MQTT PHP

Question

<?php
    $_HOST = 'IPaddress';
    $_PORT = 1883;      // Use port 8883 for SSL
    $_TOPIC = 'topicToPublishOn';
    $_PAYLOAD = $str; 
    $_QOS = 0;
    $client = new Mosquitto\Client("myClient");
    $client->connect($_HOST, $_PORT);
    $client->publish($_TOPIC, $_PAYLOAD)
    $client->loop();
?>

I do not want to open a connection every time I call this file. If a connection to the server is already present, I should be able to just go ahead and publish my data.