Modification of PHP to save data

Have a custom PHP cart system - and the current set up does not save the cart information unless the process fully completes. We want to save the name - email adddress - etc as soon as the contact information is completed regardless if the sale completes. Ideally - we could have in a seperate data file and then show if the sale completed, if not - why (failed CC or user stopped - etc) We want to then follow up with those users that abandon their carts for no apparent reason.