无法使用PHP [活动]向Bootstrap下拉菜单添加活动类

Overview

I have a navbar with li elements. I add the class active to the element that corresponds to a variable $page.

For each of the list elements, I place code similar to this:

<li<?= $page=="new" ? " class='active'" : null ?>><a href="<?= $rootUrl ?>?page=new">New event</a></li>

That way, using this example, if the $page is "new", I add the active class to the li element.

This works with top-level list items as well as dropdown children.

Issue

I want the parent element of the dropdown children to also show the active class when one of its children is active.

To do this with a dropdown with page values "new", "existing" and "gateway", I use:

<li class="dropdown<?= $page=="new"||$page=="existing"||$page="gateway" ? " active" : null ?>">

However, this doesn't work; when inspecting the element in the Chrome developer tools, the only class is dropdown1 and any other added classes have disappeared.

Adding the active class manually in Chrome developer tools produces the correct result.

Full code

<div id="navbar" class="navbar-collapse collapse">
    <ul class="nav navbar-nav">
        <li<?= $page=="dashboard" ? " class='active'" : null ?>><a href="<?= $rootUrl ?>?page=dashboard">Dashboard</a></li>
        <li class="dropdown<?= $page=="new"||$page=="existing"||$page="gateway" ? " active" : null ?>">
            <a href="javascript:void(0)" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="false">Events <span class="caret"></span></a>
            <ul class="dropdown-menu">
                <li<?= $page=="new" ? " class='active'" : null ?>><a href="<?= $rootUrl ?>?page=new">New event</a></li>
                <li<?= $page=="existing" ? " class='active'" : null ?>><a href="<?= $rootUrl ?>?page=existing">Existing events</a></li>
                <li<?= $page=="gateway" ? " class='active'" : null ?>><a href="<?= $rootUrl ?>?page=gateway">Gateway</a></li>
            </ul>
        </li>
        <li><a href="<?= $rootUrl ?>?logout=true">Sign out</a></li>
    </ul>
</div>

Question

How can I make the parent element of the dropdown have active class when one of its child elements has the active class?

</div>

You are missing a "=" at $page="gateway" should be $page=="gateway"

<li class="dropdown<?= $page=="new"||$page=="existing"||$page="gateway" ? " active" : null ?>">