Module 'apcu' already loaded in Unknown:0

[ashkan.khalili]

hello everyone ... 

Today i have just update WHMCS to 8.3.1 and after update, when i try to login to admin or even as a client, on clientarea.php shows an error like this : 

Whoops\Exception\ErrorException: Module 'apcu' already loaded in Unknown:0
Stack trace:
#0 /home/..../public_html/hub/vendor/whmcs/whmcs-foundation/lib/Utility/Error/Run.php(0): WHMCS\Utility\Error\Run->handleError(32, 'Module 'apcu' a...', 'Unknown', 0)
#1 [internal function]: WHMCS\Utility\Error\Run->handleShutdown()
#2 {main}

when i reload the page for several times, it redirects to "mysite.com/login" and gets user/password and then when i enter the user/pass again shows the same error ...!!!!

i have tried a lot to find something but nothing is out there ! ! ! 

 

would you guys please help me solve this problem !? 

 

Thanks in advance