Updated Laravel 8 to 9. Had to install php 8.0 with extensions (below) and switch php version.
Installing php. apt installs php to /etc/php
Find ini file – php -i | grep php.ini or php --ini
sudo apt install php8.0-curl php8.0-xml php8.0-mbstring php8.0-mysql php8.0-intl – installs two extensions.
Call to undefined function… See if all necessary extensions are installed