Solution:
There’re few things to do to fix this error
- Make sure you install php-mysql extension on your server In unbuntu use these commands:apt-get update apt-get install php7.0-mysql service apache2 restart
- Enable php-mysql extension in php.ini file
- Restart apache to make it work
Did you finish the step 1? I suggest this tutorial with detailed step by step that may help you out: https://wooexplorer.com/php-installation-missing-the-mysql-extension-required-by-wordpress/