错误信息如下
W: GPG error: http://ppa.launchpad.net/ondrej/php/ubuntu xenial InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 4F4EA0AAE5267A6C
解决办法, 缺什么加什么
apt-key adv --recv-keys --keyserver keyserver.ubuntu.com 4F4EA0AAE5267A6C