public function checkCollation ($encoding = 'utf8', $exception = true)
		{
			$variables = [
				'character_set_client',
				'character_set_connection',
				'character_set_database',
				'character_set_results',
				'character_set_server',
				'character_set_system',
				'collation_connection',
				'collation_database',
				'collation_server'
			];
			foreach ($variables as $variable)
			{
				$sql = "show variables like '" . $variable . "'";
				$value = $this->db->createCommand($sql)->queryOne();
				$pos = StringHelper::pos($value[ 'Value' ], $encoding);
				if ($pos !== 0)
				{
					if (!$exception)
						return false;
					else
						throw new InvalidConfigException ("Parameter $variable does not match $encoding.");
				}
			}

			return true;
		}