php ini unserialize_callback_func

The unserialize callback function will be called (with the undefined class name as parameter), if the unserializer finds an undefined class which should be instantiated.

A warning appears if the specified function is not defined, or if the function doesn't include/implement the missing class. So only set this entry, if you really want to implement such a callback-function.

unserialize_callback_func =

This directive allows you to control the response of the unserializer when a request is made to instantiate an undefined class.

For most users, this directive is irrelevant because PHP already outputs a warning in such instances if PHP's error reporting is tuned to the appropriate level.