$discord->on('ready', function (Discord $discord) use($pdo) {
    $channel = $discord->getChannel('id');
    while (true) {
        if (thereIsANewAchievementToSend()) { 
            $channel->sendMessage($achievement->text);
        }
        sleep(5);
    } 
});

while (true) {
$discord = new Discord(...);

$discord->on('ready', function (Discord $discord) use($pdo) {
    $channel = $discord->getChannel('id');
    while (true) {
        if (thereIsANewAchievementToSend()) { 
            $channel->sendMessage($achievement->text);
        }
        sleep(5);
    } 
     $discord->close();
});
$discord->start();

}