I am not able to upgrade to php7.3 from 7.2 on ubuntu 16.04, I run the following commands :
sudo apt-get install python-software-properties
sudo LC_ALL=C.UTF-8 add-apt-repository ppa:ondrej/php
sudo apt-get update
sudo apt install php7.3
with th following output appears:
Building dependency tree
Reading state information... Done
Note, selecting 'php7.3-mongodb' for regex 'php7.3'
Note, selecting 'php7.3-memcached' for regex 'php7.3'
Note, selecting 'php7.3-msgpack' for regex 'php7.3'
Note, selecting 'php7.3-igbinary' for regex 'php7.3'
Note, selecting 'php7.3-uploadprogress' for regex 'php7.3'
Note, selecting 'php-uploadprogress' instead of 'php7.3-uploadprogress'
php7.3-msgpack is already the newest version (2.1.1+0.5.7-2+ubuntu16.04.1+deb.sury.org+4).
php7.3-mongodb is already the newest version (1.8.1-2+ubuntu16.04.1+deb.sury.org+4).
php7.3-memcached is already the newest version (3.1.5+2.2.0-4+ubuntu16.04.1+deb.sury.org+4).
php-uploadprogress is already the newest version (1.0.3.1-4-g95d8a0f-5+ubuntu16.04.1+deb.sury.org+10).
php7.3-igbinary is already the newest version (3.1.6+2.0.8-2+ubuntu16.04.1+deb.sury.org+4).
0 upgraded, 0 newly installed, 0 to remove and 10 not upgraded.
and PHP -v still the old version
Ondřej has removed support for 16.04 just a few days ago:
As of this moment, all the packages for the Ubuntu 16.04 LTS (Xenial) have been removed from the repositories.
This explains how it worked ok for you last week, but isn't working today.