Silverstripe Sessions or URL Parameters - session

Question

I'm trying to figure out how to pass a value from my .ss page to my controller for a custom search filter that I've built. The idea is you click on this image or a form button and then the page will set a session variable and refresh itself. Upon page load the page loads different information depending on what it reads in the session variable. I can accomplish the same thing with URL Parameters but there are no examples online that I could find that would show me how to do this.
Basically I have this as my php:
class ArticleHolder_Controller extends Page_Controller {
public function ValidateType(){
if(isset($_SESSION['mySearchTag']) && !empty($_SESSION['mySearchTag'])) {
$tag = $_SESSION['mySearchTag'];
}
else{
$tag='News';
}
$filter = $this::get()->filter('Filters:PartialMatch', $tag)->First();
if ($filter == NULL){
return NULL;
}
else{
$_SESSION['mySearchTag']=$tag;
return $this->PaginatedPages();
}
}
public function PaginatedPages(){
$paginatedItems = new PaginatedList($this->filterArticles($_SESSION['mySearchTag']), $this->request);
$paginatedItems->setPageLength(3);
return $paginatedItems;
}
public function filterArticles($tag){
return ArticlePage::get()->filter('category:PartialMatch', $tag)->sort('Date DESC');
}
}
my .ss looks like this:
<% if ValidateType() %>
<ul>
<% loop $PaginatedPages %>
<li>
<div class="article">
<h2>$Title</h2>
<h3>$Date</h3>
<img class="indent" src="$Photo.link" alt="image"/>
<p class="indent">$Teaser</p>
</div>
</li>
<% end_loop %>
</ul>
<% include Pagination %>
<% else %>
<p>SORRY NO RESULTS WERE FOUND</p>
<% end_if %>
This code works as is. What I cannot figure out how to now add a clickable button on .ss page that will reload the page and set a session variable value.
If I can achieve this with url parameters then that can work too, I just need to know how to set them in the .ss page and how to retrieve them in the php.

Answer 1

Create a SetFilter function that will take the URL parameter ID and set it to your session variable:
public function SetFilter() {
if($this->request->param('ID')) {
$_SESSION['mySearchTag'] = $this->request->param('ID');
}
return array();
}
Make sure your SetFilter function is added to the $allowed_actions of your controller:
static $allowed_actions = array (
'SetFilter'
);
This function is called by your page link followed by /SetFilter/[your-filter].
In your template you would create a link to create this filter like so:
Filter articles by example