for testing purpose i integrated , paypal sand box in my code, i am doing onlline car shop project

now lets suppose , Customers visits my website, and he has to pay before entering my website, so for that purpose i just used PAYPAL sand box with merchant and buyer accounts,

now i want to know that when user pays the amount then i want to keep that record in m sql db too, and how would i know that whom how much paid and how would i keep record of it and how i wuld get informed

and please help me, i checked almost all links regarding PAYPAL and but didn't help so please help must , no link please

just by using dll and sandbox's parameters