To enable MySQLi, view Editing the Core config.php File.
The Core config.php contains two advanced settings that you may need when MySQLi is in use. These settings are to be ignored as long as you are not having issues of the following type:
MySQL Error : Illegal mix of collations (latin1_swedish_ci,COERCIBLE) and (utf8_general_ci,IMPLICIT) for operation
From the Administrator Control Panel, go to Admin CP->Maintenance->Execute SQL Query. If you receive a no permissions message, please refer back to Editing the vBulletin Configuration File on how to grant the appropriate permissions so that you may execute queries.
Enter the following query in the Manual Query input box and press
SHOW VARIABLES LIKE 'char%'
Note:
If the values are the same, then your problem will not be solved by this solution. Please contact vBulletin Support in this case. You may have tables in your database that are configured to use a different character set than your database is. All of your tables will need to be updated to use the same character set. This condition can be caused by changing the character set of your database after vBulletin has been installed. Upgrades may create tables that are in your new character set, which will cause problems.
Create a new file in your forums include directory named mysqli.ini. Inside of this file place:
[client] default-character-set=utf8
Edit the vBulletin Configuration File file by following the instructions in the previous section.
Uncomment the following line by removing the two slashes from the beginning
// $config['Mysqli']['ini_file'] = 'c:\program files\MySQL\MySQL Server 4.1\my.ini';
$config['Mysqli']['ini_file'] = 'c:\program files\apache group\apache\htdocs\forums\includes\mysqli.ini';