php 记录错误日志

/**
 * 记录错误日志
 * @param 日志内容  $res
 */
function save_log($res) {
    $err_date    = date("Ymd", time());
    $address    = '/home/wwwroot/itservice/backend/tools';
    if (!is_dir($address)) {
        mkdir($address, 0700, true);
    }
    $address    = $address.'/'.$err_date . '_autoload_itservice.log';
    $error_date = date("Y-m-d H:i:s", time());
    if(!empty($_SERVER['HTTP_REFERER'])) {
        $file = $_SERVER['HTTP_REFERER'];
    } else {
        @$file = $_SERVER['REQUEST_URI'];
    }
    if(is_array($res)) {
        $res_real = "$error_date\t$file\n";
        error_log($res_real, 3, $address);
        $res = var_export($res,true);
        $res = $res."\n";
        error_log($res, 3, $address);
    } else {
        $res_real = "$error_date\t$file\t$res\n";
        error_log($res_real, 3, $address);
    }
}