The behaviour of these functions is affected by settings in php.ini.
|unserialize_callback_func||NULL||PHP_INI_ALL||Available since PHP 4.2.0.|
Here's a short explanation of the configuration directives.
- unserialize_callback_func string
The callback specified is called when unserialize() attempts to use an undefined class. A warning appears if the specified callback function is not defined, or if the callback function fails to define the missing class.