What to Do When "Failed to fetch http://ppa.launchpad.net/ondrej/php5-5.6/ubuntu/dists/trusty/main/binary-amd64/Packages 404 Not Found" Occurs

On Ubuntu,

sudo apt update

If you encounter

Failed to fetch http://ppa.launchpad.net/ondrej/php5-5.6/ubuntu/dists/trusty/main/binary-amd64/Packages 404 Not Found

then

sudo add-apt-repository ppa:ondrej/php

sudo rm /etc/apt/sources.list.d/ondrej-php5-5_6-trusty.list
sudo add-apt-repository ppa:ondrej/php5-5.6 --remove --yes

sudo apt update