displaying a page via multiple variables in url
===

a sample of my link would look like this "/jet/index.php?year=2011&quarter=Q1"
now i need to display the page that contains the first months in quarter one of year 2011.
/jet/index.php?year=2011&quarter=Q1 would display april may june. and so on.

my code looks like this
   

     <a href="index.php?year=2011&quarter=Q1">
        <a href="index.php?year=2011&quarter=Q2">
        <a href="index.php?year=2011&quarter=Q1">
        <a href="index.php?year=2011&quarter=Q4">

my home page, which is the year 2012 works just fine, here is the code
   

     <?php 
    $quarters = array('Q1' => 'firstq2012.php', 'Q2' => 'secondq2012.php', 'Q3' => 'thirdq2012.php', 'Q4' => 'fourthq2012.php');
    if(isset($_GET['quarter'])) {
        if(in_array($_GET['quarter'], array_keys($quarters))) {
            include_once $quarters[$_GET['quarter']];
        } else {
            header('Location: 404.php');
        }
    } else {
        include_once $quarters['Q3'];
    }
    ?>

i need your help on how would the transition from 2012 to 2011 would look like (i do it via a link)

thanks!