在另一个类中调用函数不起作用

快速的菜鸟问题。我正在尝试调用另一个类中的函数，但它不起作用。提前致谢

** main.php **
require_once("../push/push.php"); 
new APNS_Push($config);
start();

** push.php **
class APNS_Push
{
private $fp = NULL;
private $server;
private $certificate;
private $passphrase;
function __construct($config)
{
    $this->server = $config['server'];
    $this->certificate = $config['certificate'];
    $this->passphrase = $config['passphrase'];
    // Create a connection to the database.
    $this->pdo = new PDO(
        'mysql:host=' . $config['db']['host'] . ';dbname=' . $config['db']['dbname'], 
        $config['db']['username'], 
        $config['db']['password'],
        array());

    // If there is an error executing database queries, we want PDO to
    // throw an exception.
    $this->pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    // We want the database to handle all strings as UTF-8.
    $this->pdo->query('SET NAMES utf8');
}
// This is the main loop for this script. It polls the database for new
// messages, sends them to APNS, sleeps for a few seconds, and repeats this
// forever (or until a fatal error occurs and the script exits).
function start()
{
    //writeToLog('Connecting to ' . $this->server);
    if (!$this->connectToAPNS())
        exit;

        // Do at most 20 messages at a time. Note: we send each message in
        // a separate packet to APNS. It would be more efficient if we 
        // combined several messages into one packet, but this script isn't
        // smart enough to do that. ;-)
        $stmt = $this->pdo->prepare('SELECT * FROM push_queue WHERE time_sent IS NULL LIMIT 25');
        $stmt->execute();
        $messages = $stmt->fetchAll(PDO::FETCH_OBJ);
        $deletedIds = array();
        foreach ($messages as $message)
        {
            echo 's'; 
            if ($this->sendNotification($message->message_id, $message->device_token, $message->payload))
            {
                //$stmt = $this->pdo->prepare('UPDATE push_queue SET time_sent = NOW() WHERE message_id = ?');
                $name = $message->name; 
                echo $name; 
                $value = '1'; 
                //$this->pdo->query('UPDATE users SET needsUpdate = '$value' WHERE username='$name'');
                //$stmt->execute(array($message->message_id));
                 $deletedIds[] = $message->message_id;
                //$stmt = $this->pdo->prepare('DELETE FROM push_queue WHERE message_id = ?');
                //$stmt->execute(array($message->message_id));
            }
            else  // failed to deliver
            {
                $this->reconnectToAPNS();
            }
        }
        //Delete the chunk of messages.
        $this->pdo->query('DELETE FROM push_queue WHERE message_id IN ('.implode(',', $deletedIds).')');

        //echo 'success'; 
        unset($messages);           
}