How to fix Debian 9 apt-get update error: The following signatures were invalid: EXPKEYSIG B188E2B695BD4743 DEB.SURY.ORG Automatic Signing Key
To fix error we need download and install new SURI repository key:
# wget -O /etc/apt/trusted.gpg.d/php.gpg https://packages.sury.org/php/apt.gpg
And try re-run update:
# apt update
# apt upgrade
Now problem should be fixed
Cheers!
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