Sometimes people receiving this kind of error : Fatal error: Call to undefined function mb_convert_encoding() in /public_html/this/this.php at line 188. Normally this kind of errors comes in PHP Sites and PHP framework aswell.
It looks like PHP mbstring not installed on your server.
Solution :
In my case I have just uncomment ;extension=php_mbstring.dll in php.ini file and issue has been resolved.
Don't forget to restart apache server after uncomment ;extension=php_mbstring.dll