i have created a custom form right now – which basically works great for subscribing. But i want to request on loading the form if the user is already subscribed to some lists so i can mark the correct list checkboxes as checked.
Unfortunately i currently cannot find the documentation regarding API calls. There surely is a php function or something else i can call to retrieve whether a user is subscribed to a list ID or not? Maybe you can point me to the correct documentation section?