i have a Custom Cart Page which i have built its pretty standard, what i am trying to do is send all the ids of the items in the cart when the user clicks checkout so the user flow is as follows:
1) User Click Checkout 2) Packages added to table one row each item with waiting payment status. 3) User goes to paypal and pays 4) Paypal Ipn picks up payment and order ids via custom field and updates payment status of orders.
So essentially the paypal pay will be a single total payment as opposed to displaying each item. Is it possible to send all item ids via one custom field or do i have to implement a cart style paypal feature which i don't really want to?
I don't see any reason why you can't put a series of Id values in the custom field, perhaps comma separated, but it is only 255 characters long. You would have to parse the field in your IPN handler to separate out the id values again.
But I would suggest using PayPal's cart handling instead, there are no problems with how many items you have to process and also the customer sees a proper list of the items they have bought when they go through the PayPal payment process. More robust and friendlier to the user.
You may find PayPal's Third Party Shopping Cart documentation useful