Before the question, I am running on Ubuntu 16.04. Upgrading is not an immediate option. I have installed php5.6 following the instructions in this article: https://www.liquidweb.com/kb/install-multiple-php-versions-on-ubuntu-16-04/
Following those steps has worked in that phpinfo() shows 5.6, but when using phpmyadmin I get this error: The mbstring extension is missing. Please check your PHP configuration.
After trying to install the package by itself
apt-get install php5.6-mbstring
I get this error:
E: Unable to locate package php5.6-mbstring
E: Couldn't find any package by glob 'php5.6-mbstring'
E: Couldn't find any package by regex 'php5.6-mbstring'
I have seen a lot of solutions, but none seem to fix this issue or are current. Any help would be appreciated, or if this is something that can no longer be done that would good to know as well. Thanks!