how to fix - Fatal error: Uncaught Error: Call to undefined function mb_convert_encoding()
I use the php readability library in some of my code, and found on a new server that it was throwing the error.
Fatal error: Uncaught Error: Call to undefined function mb_convert_encoding()
For me this was caused on Debian from php missing the extention:
php-mbstring php7.0-mbstring
which can be installed in debian by using the following command:
sudo apt-get install php-mbstring