codeigniterinputpost汉语不能提交

function _clean_input_keys($str)
        {
                if ( ! preg_match("/^[a-z0-9:_/-]+$/i", $str))
                {
                        exit('Disallowed Key Characters.');
                }
 
                // Clean UTF-8 if supported
                if (UTF8_ENABLED === TRUE)
                {
                        $str = $this->uni->clean_string($str);
                }
 
                return $str;
        }