Warning message after implementation

[duksis]

After adding SessionHandlerCookie to the code my logs got flooded with these messages

NOTICE: PHP message: PHP Warning:  session_write_close(): Session callback expects true/false return value in Unknown on line 0
NOTICE: PHP message: PHP Warning:  session_write_close(): Failed to write session data using user defined save handler. (session.save_
path: /tmp) in Unknown on line 0

I'm running php 7.3.33