Drupal 7 ignoring $_SESSION in template

Question

I'm working on a simple script in a custom theme in Drupal 7 that is supposed to just rotate through different background image each time a user loads the page. This is my code in [view].tpl.php that picks which image to use.

$img_index = (!isset($_SESSION["img_index"]) || is_null($_SESSION["img_index"])) ? 1 : $_SESSION["img_index"] + 1;
if ($img_index > 2) {
 $img_index = 0;
}

$_SESSION["img_index"] = $img_index;

Pretty simple stuff, and it works fine as long as Drupal starts up a session. However, if I delete my session cookie, then always shows the same image, a session is never started.

I'm assuming that since this code is in the view file that the view code is being cached for anonymous users and hence the session is never started, but I can't figure out how to otherwise do what I want.

Answer 1

Don't mess with session like /u/maiznieks mentioned on Reddit. It's going to affect performance.

I've had to do something similar in the past and went with an approach like /u/maiznieks mentions. It's something like this,

• Return all the URLs in an array via JS on Drupal.settings.
• Check if a cookie is set.
  • If it's not, set it and set it's value to 0.
  • If it's set, get the value, increase the value by one, save it to the cookie.
• With that value, now you have an index.
• Check if image[index] exists
  • If it does, show that to the user.
  • If it doesn't, reset index to 0 and show that. Save 0 to the cookie.

You keep caching. You keep showing the user new images on every page load.

You could set your current view to do a random sort every 5 mins. You would then only have to update the logic above to replace that image. That way you can keep something similar working for users with no JS but still keep this functionality for the rest.

You can replace cookies above with HTML5 local storage if you'd like.

Answer 2

@hobberwickey, I will suggest to create a custom module and implement hook_boot() in module. As per drupal bootstrap process session layer will call after cache layer everytime. hook_boot can be called in cache pages and before bootstrap process also. You can take more information here.