An exploration of php sessions and databases with a little bit of jquery thrown in. Started from this source: https://www.codeofaninja.com/2013/04/shopping-cart-in-php.html, and grew it from there. Probably not idiomatic of php or javascript (still learning web-based stuff), definitely not production standard code. Key word is 'exploration'.
Todo: make transitions with jquery ajax calls instead of all new pages https://www.w3schools.com/jquery/jquery_ajax_load.asp