How can I save a transaction id in a cookie using PHP and Shopify events?

[MadAgos]

Hi everyone, I'm currently working on a Shopify app and I need to save a transaction id from an external source in a cookie using PHP. The id is passed as a parameter in the query string of the URL. I've tried using JavaScript, but Shopify blocks cookies after 7 days. Can anyone suggest a way to accomplish this using PHP and Shopify events? Thanks in advance for your help!