public static function init($conf)
 {
     if (!file_exists($conf->dir)) {
         if (!mkdir($conf->dir, 0777, true)) {
             echo "[fail to init log][can not mkdir][path: {$conf->dir}]<br>";
             return false;
         }
     }
     $ret = ub_log_init($conf->dir, $conf->file, $conf->severity, $conf->format, $conf->flush);
     if (!$ret) {
         return $ret;
     }
     //        self::$_logfile = fopen("$conf->dir/$conf->file", "a+");
     //        echo "[start log][write log to $conf->dir/$conf->file]<br>";
     self::$_severity = $conf->severity;
     self::$_disable_ostream = $conf->disable_ostream;
     self::$_logconf = $conf;
     return true;
 }