code: public static function toXml($values)
      {
          if (!is_array($values) || count($values) <= 0) {
              return false;
          }
  
          $xml = "<xml>";
          foreach ($values as $key => $val) {
              if (is_numeric($val)) {
                  $xml.="<".$key.">".$val."</".$key.">";
              } else {
                  $xml.="<".$key."><![CDATA[".$val."]]></".$key.">";
              }
          }
          $xml.="</xml>";
          return $xml;
      }
docs: 输出xml字符
  @param array $values
  @return string|bool