Notice: main() [function.main]: The script tried to execute a method or access a property of an incomplete object. Please ensure that the class definition "<classname>" of the object you are trying to operate on was loaded _before_ unserialize() gets called or provide a __autoload() function to load the class definition in <filename> on line <line>

You get this error if you have and object in your $_SESSION array and you call session_start() before you have loaded your included classes.

如果在session中存储了类对象，不能在调用这个类之前，使用session_start().

如果你php.ini文件中开启了

session.auto_start = 1

也不行