I'm using paypal adaptive payments for my website. I send request to the https://svcs.sandbox.paypal.com/AdaptivePayments/Pay, then redirect user and process order in my IPN return function. 
But now i want to add some information about order items. As i learned from here, i must use embedded flow only. So, i must call Pay with actionType=CREATE, then call SetPaymentOptions...
At this point, i don't understand what i should do now. Should i process IPN as i did earlier, or i must make ExecutePayment request? And when i must make this ExecutePayment request?
Have you some full working example for Embedded Flow with actionType=CREATE and ExecutePayment, preferable for PHP.