PHP 运行系统命令打包

public function download() {
        system('ssh root@**.**.**.** \n g7f8f9d90s0s8');
        system("cd /data/logs/{$_POST['server']}");
        system("tar -zcvf /var/ftp/{$_POST['server']}_{$_POST['date']}.tar.gz ./*{$_POST['date']}*.log", $out);
        if ($out != false) {
            system("touch 已打包完成.txt");
        }
        system("exit");
    }