CraftCMS > UserSessionService should be compatible with CWebUser I've migrated my Craft project from CentOS/PHP5 to Ubuntu/PHP7 ---  since then I'm seeing this message in /craft/storage/runtime/logs/phperrors.log

[14-Jun-2017 14:40:49 UTC] PHP Warning:  Declaration of Craft\UserSessionService::login($username, $password, $rememberMe = false) should be compatible with CWebUser::login($identity, $duration = 0) in /home/hidden/craft/app/services/UserSessionService.php on line 17
[14-Jun-2017 14:40:49 UTC] PHP Warning:  Declaration of Craft\UserSessionService::afterLogin() should be compatible with CWebUser::afterLogin($fromCookie) in /home/hidden/craft/app/services/UserSessionService.php on line 17
[14-Jun-2017 15:50:53 UTC] PHP Warning:  Declaration of Craft\UserSessionService::login($username, $password, $rememberMe = false) should be compatible with CWebUser::login($identity, $duration = 0) in /home/hidden/craft/app/services/UserSessionService.php on line 17
[14-Jun-2017 15:50:53 UTC] PHP Warning:  Declaration of Craft\UserSessionService::afterLogin() should be compatible with CWebUser::afterLogin($fromCookie) in /home/hidden/craft/app/services/UserSessionService.php on line 17
[14-Jun-2017 16:03:04 UTC] PHP Warning:  Declaration of Craft\UserSessionService::login($username, $password, $rememberMe = false) should be compatible with CWebUser::login($identity, $duration = 0) in /home/hidden/craft/app/services/UserSessionService.php on line 17
[14-Jun-2017 16:03:04 UTC] PHP Warning:  Declaration of Craft\UserSessionService::afterLogin() should be compatible with CWebUser::afterLogin($fromCookie) in /home/hidden/craft/app/services/UserSessionService.php on line 17


Any Help?
It's a known issue you can safely ignore on Craft 2, that's been resolved for Craft 3.

PHP 7.0 (or maybe it was 7.1) changed the way that particular error was reported from E_STRICT (which Craft 2 is suppressing) to E_WARNING, which Craft 2 isn't suppressing, so now it pops up on latter versions of PHP.