Sometimes we get MySQL extension is missing errors on our server which is very painful. so in this tutorial, you can very easily fix this error. Just run the command described in the video and this error will be fixed.
Step 1. Check PHP version
php -v
Step 2. Change the PHP version according to your server's PHP version. That you get in the first step.
sudo apt-get install php7.4-mysql
Step 3. Restart your Apache server
sudo systemctl restart apache2