How can I log a record??

Hello, I am using PHP4 + mysql + Apache to do a little project, Now, I want to let the end user can browse the record in a database table. Someone may want the record, through my php script interface, how can I log the record, which the user is editing and going to save it. Or at least how can other instance process know that the record is using by some other . So that the script can warn the user not to edit the record. Thanks! Zenith