Problem set tracker Announce

[htschannerl]

Hello,

I'm trying to change the tracker annouce. Here is the code:

foreach ($trackers as $tracker){
        $scrapeold = $tracker->getScrape();
        $announceold = $tracker->getAnnounce();

        echo $announceold . "<br><br>";

        $announcenew = str_replace("http://", "http://", $announceold);

        $tracker->setAnnounce($announcenew);
        echo $tracker->getAnnounce() . "<br>";
    }

But is not work.