code: public static function sysGetTempDir()
      {
          if (self::$useUploadTempDirectory) {
              //  use upload-directory when defined to allow running on environments having very restricted
              //      open_basedir configs
              if (ini_get('upload_tmp_dir') !== false) {
                  if ($temp = ini_get('upload_tmp_dir')) {
                      if (file_exists($temp)) {
                          return realpath($temp);
                      }
                  }
              }
          }
  
          return realpath(sys_get_temp_dir());
      }
docs: Get the systems temporary directory.
  
  @return string