A collection of 19 tips on understanding and using sessions in PHP. Clear explanations and tutorial exercises are provided on starting and closing sessions, saving and retrieving values in sessions, deciding how session IDs to be transferred, deciding where to store session files, deciding when to expire session values, etc. Topics included in this collections: What Is a Session? How To Turn On the Session Support? How To Save/Retrieve Values to the Current Session? What Is a Session ID? How To Retrieve the Session ID of the Current Session? What Are the Options to Transfer Session IDs? How Session IDs Are Transferred on Your Web Server? How To Force the PHP Engine to Use Cookies to Transfer Session IDs? Is It More Secure to Use Cookies to Transfer Session IDs? Where Are the Session Values Stored? What Set the Timeout Period on Session Values? How To Remove Values Saved in the Current Session? How To Tell If a Session Is New? What Is session_register()?