Add some html/js code to pages via hooks

Add this code to site.php file:

Am_Di::getInstance()->hook->add(Am_Event::AFTER_RENDER, function (Am_Event_AfterRender $event) {
    static $contentAdded = false;
    if ($contentAdded) return;

    // Do it only for a specific URL.
    if (!preg_match('#^/amember/helpdesk/index.*#i', $_SERVER['REQUEST_URI'])) {
        return;
    }

    $contentAdded = (bool)$event->replace(
        '#(<h1>Tickets.*</h1>)#i',
        '$1<div>Some content</div>',
        1
    );
});