PHP ssh->exec() Keep Alive util code completes its job

For sending campaign email we are using ssh->exec but if mails are more than 10k means without any message its stops working

So I need to keep alive file running. How to fix?.

$ssh = new SSH2('example.com');

if (!$ssh->login('username', 'password')) {

 exceptionErrorHandler("Error logging in to server for " . $queue);
} else {
 $ssh->exec('php applications/root/public_html/includes/php/workers/' . $queue . '.php &');
}