sudo add-apt-repository -y ppa:ondrej/php
Ign:1 http://archive.ubuntu.com/ubuntu trusty InRelease
Get:2 http://security.ubuntu.com/ubuntu bionic-security InRelease [83.2 kB]
Ign:3 http://ppa.launchpad.net/ondrej/mysql-5.6/ubuntu bionic InRelease
Hit:4 http://archive.ubuntu.com/ubuntu trusty Release
Hit:5 http://ppa.launchpad.net/ondrej/php/ubuntu bionic InRelease
Err:6 http://ppa.launchpad.net/ondrej/mysql-5.6/ubuntu bionic Release
  404  Not Found [IP: 91.189.95.83 80]
Hit:8 http://ams2.mirrors.digitalocean.com/ubuntu bionic InRelease
Hit:9 http://ams2.mirrors.digitalocean.com/ubuntu bionic-updates InRelease
Hit:10 http://ams2.mirrors.digitalocean.com/ubuntu bionic-backports InRelease
Reading package lists... Done
E: The repository 'http://ppa.launchpad.net/ondrej/mysql-5.6/ubuntu bionic Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

sudo apt-get purge php *
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package bin
E: Unable to locate package boot
E: Unable to locate package dev
E: Unable to locate package etc
E: Unable to locate package home
E: Unable to locate package initrd.img
E: Couldn't find any package by glob 'initrd.img'
E: Couldn't find any package by regex 'initrd.img'
E: Unable to locate package initrd.img.old
E: Couldn't find any package by glob 'initrd.img.old'
E: Couldn't find any package by regex 'initrd.img.old'
E: Unable to locate package lib
E: Unable to locate package lib64
E: Unable to locate package lost+found
E: Couldn't find any package by regex 'lost+found'
E: Unable to locate package media
E: Unable to locate package mnt
E: Unable to locate package proc
E: Unable to locate package root
E: Unable to locate package run
E: Unable to locate package sbin
E: Unable to locate package srv
E: Unable to locate package sys
E: Unable to locate package tmp
E: Unable to locate package usr
E: Unable to locate package var
E: Unable to locate package vmlinuz
E: Unable to locate package vmlinuz.old
E: Couldn't find any package by glob 'vmlinuz.old'
E: Couldn't find any package by regex 'vmlinuz.old'