lib/Request.php:196: Warning[2]: session_start(): open(/tmp/sess_1837f93082c2632cae37b7a8b3ac3ec0, O_RDWR) failed: Permission denied (13)
Basically, using techniques from sociology and psychology to see if what you plan to design or have designed is usable by your intended users (that's my definition, don't quote me :-)
Unknown:0: Warning[2]: Unknown(): open(/tmp/sess_1837f93082c2632cae37b7a8b3ac3ec0, O_RDWR) failed: Permission denied (13)
Unknown:0: Warning[2]: Unknown(): Failed to write session data (files). Please verify that the current setting of session.save_path is correct (/tmp)