mb_internal_encoding() error after enabling in php.ini in Windows 10

I have php verison 5.6.8. I enabled php_mbstring.dll fom php.ini. I have also php_mbstring.dll in extension folder. I enabled and restart apache and windows also. But I still get an error like this: Call to undefined function Illuminate\Foundation\Bootstrap\mb_internal_encoding() in ..\vendor\laravel\framework\src\Illuminate\Foundation\Bootstrap\LoadConfiguration.php on line 43. How can this be solved? Thanks in Advace.