I haven't coded anything web in a few years, so forgive me if I'm rusty but:
You can't do this all serverside. The page will compile but unless the user refreshes the page, the object in question will be forever available.
What you want to do, is use kekub's example to generate the following code only if it's within the time range, but also include JavaScript to destroy it when time is up:
$time = date("i");
if($time < 10){
$timeToExpire = 10 - $time;
echo "<div id="yourObject">I will expire soon!</div>;
echo"<script type = 'text/javascript'>setTimeout(function() {
$('#yourObject').fadeOut('fast');
}, ".$timeToExpire * 10000.");</script>"; // * milliseconds e.g 6 minutes
}
I haven't tested it but what should happen is, the webpage will generate the div and also the code needed to hide it when the time is up (say there is only 6 minutes left to show it).
Although I think personally you should do this all in Javascript.