This method should release the exclusive lock that was acquired by the open() method.
Note that this will effectively serialize parallel requests, which affects performance for a single user session.
Not locking the resource would on the other hand allow for race conditions if two or more parallel requests change the session data.
(PHP 5 >= 5.4.0)
SessionHandlerInterface::close — Close the session
Closes the current session. This function is automatically executed when closing the session, or explicitly via session_write_close().
This function has no parameters.
The return value (usually
TRUE on success,
FALSE on failure). Note this value is returned internally to PHP for processing.