Problems related to session storage in databases and memcache

When the session is stored in the database and memcache, the following Warning is reported when the session information is stored in the database and memcache. if the information cannot be stored, how can this problem be solved? Warning: & nbsp; Invalid & nbsp; callback & nbsp; Session_mem: write, & nbsession problems in database and memcache
The following warning is displayed when session information is stored in the database and memcache. The information cannot be stored. how can this problem be solved?
Warning: Invalid callback Session_mem: write, class 'session _ mem 'not found in Unknown on line 0

Warning: Unknown: Failed to write session data (user). Please verify that the current setting of session. save_path is correct (C:/temp) in Unknown on line 0

Warning: Invalid callback Session_mem: close, class 'session _ mem 'not found in Unknown on line 0
------ Solution --------------------
Session_mem this class cannot be found
Check the value of session. save_path in PHP. INI.