Sometime when we try to access session object we get the object class as __PHP_Incomplete_Class. This happens when we try to initialize the session before loading the class definitions for the object we are trying to save into the session. To say it in simple, if class definitions are not defined, PHP creates incomplete objects of the class __PHP_Incomplete_Class. To avoid __php_incomplete_class object session error, every class definition must be included or defined before starting the session This, along with other PHP basic interview questions for freshers, is a regular feature in PHP interviews, be ready to tackle it with the approach mentioned below.