Keep get parameter in all url - url

Question

I'm using prestashop and i want to run a/b test. It means you test 2 different templates of your website in the same time as the traffic is redirected 50% to templateA and 50% to templateB.
I have to theme in my folder :
-ThemeA
-ThemeB
To run the test i need to access themeB via a different url form themeA.
So in the folder "/config" i modified the file setting.inc.php like this :
if(isset($_GET['ab']))
{
define('_THEME_NAME_', 'themeB');
}
else{
define('_THEME_NAME_', 'themeA');
}
Now i can reach themeb by typing : www.myshop.com/?ab
My problem is, whenever i click a link, the ?ab parameter is lost and it goes back to template A.
I found someone using another cms that resolved to problem using this code :
`$this->redirect(array('name')); `
But i don't know how to adapt it to prestashop and where should i put it.
Any help would be very appreciated.
Thanks

Answer 1

One quick workaround might be using session, if session is started ([http://sg3.php.net/manual/en/function.session-start.php][1]) before your "theme check".
// Page => watermelons.php
<?php
session_start();
if(isset($_GET['ab']) || isset($_SESSION['ab'])) {
$_SESSION['ab'] = 'themeB';
define('_THEME_NAME_', 'themeB');
} else{
define('_THEME_NAME_', 'themeA');
}
echo _THEME_NAME_;
?>
<br />go to coconuts
// Page => coconuts.php
<?php
session_start();
if(isset($_GET['ab']) || isset($_SESSION['ab'])) {
$_SESSION['ab'] = 'themeB';
define('_THEME_NAME_', 'themeB');
} else{
define('_THEME_NAME_', 'themeA');
}
echo _THEME_NAME_;
?>
<br />go to watermelons