code: public static function toJsonString($data, $isNotUnescapedUnicode = true)
      {
          if ($isNotUnescapedUnicode !== true) {
              $r = json_encode($data);
          } else {
              if (version_compare(PHP_VERSION, '5.4.0', '<')) {
                  $r = json_encode($data);
                  $r = preg_replace_callback(
                      "#\\\u([0-9a-f]{4})#i",
                      function ($matchs) {
                          return iconv('UCS-2BE', 'UTF-8', pack('H4', $matchs[1]));
                      },
                      $r
                  );
              } else {
                  $r = json_encode($data, JSON_UNESCAPED_UNICODE);
              }
          }
          return $r;
      }
docs: 获取签名信息