PHP Manual: Get and/or set the current session module

stringfalse session_module_name(stringnull $module = null)

session_module_name gets the name of the current session module, which is also known as session.save_handler.

module: If module is specified and not null, that module will be used instead. Passing "user" to this parameter is forbidden. Instead session_set_save_handler has to be called to set a user defined session handler.

Returns the name of the current session module, or false on failure.

Version	Description
8.0.0	`module` is nullable now.
7.2.0	It is now explicitly forbidden to set the module name to `"user"`. Formerly, this has been silently ignored.