Okay, so I have a form that send the account information of the user to "sucess.php" but say I have another file called 'trade.php' and i want to use the same users information from sucess.php, how do I send over the information without making them log in again?

Like you log in, it says you've logged in, then you go to another page, but you're still keeping track of the user? Do you understand?