Write a function to pass variables onclick event to a php page

I have an already built website (written using joomla). However, there is a feature that I need but I don't know which language should be used to write the function. I've done some research and most of them suggest ajax. Any other suggestions are welcomed. This is the scenario: PHP page 1: <a href="link2.'?video='.$slide->id; ?>" target="target; ?>" alt="id; ?>" > when I click on the link, I need to set $slide->id value into a global variable which will be used in another php page (For joomla experienced, the other php page is a [login to view URL] file for a component) Of course, using $_GET['video'] only works in the href link page. But I need the variable in [login to view URL] page Obviously, the variable depends on the slide that is being clicked and it's not constant. Therefore, I assume it should be referenced with the onclick function. I hope my explanation is clear.