Conditional Includes in Template Animation

conditional_includes.txt

When the user is not logged in:

<div id="content" class="noSidebar">
    <div id="main">
        <!-- STUFF GOES IN HERE //-->
    </div>
</div>

Now imagine that for some really good technical reason, we need to remove that noSidebar class when we add a sidebar:

<div id="content" class="withSidebar">
    <div id="main">
        <!-- STUFF GOES IN HERE //-->
    </div>
    <div id="sideBar">
        <!-- SOME OTHER STUFF GOES IN HERE //-->
    </div>
</div>

The designer/template implementor simply creates two files:

my_interface.html
my_interface_logged_in.html

The developer then chooses which one to load according to whatever login system they're using:

if($security->loggedIn())
    $template = $this->loadTemplate('my_interface_logged_in.html');
else
    $template = $this->loadTemplate('my_interface.html');