PHP date question

Ok I can echo "Hello World!" but the problem is that after 30 minutes it should only echo "Hello you loser!"
How do I do this?

<?php

if( isset( $_COOKIE['time'] ) )
{
    if( time() < ( $_COOKIE['time'] + 30 * 60 ) )
    {
        echo 'Hello, World!';
    }else
    {
        echo 'Hello, you loser!';
        die;
    }
}else
{
    setcookie( 'time', time() );
    echo 'Hello, World!';
}

?>

<meta http-equiv="refresh" content="5;<?=$_SERVER['PHP_SELF'];?>" />