Your PHP installation appears to be missing the MySQL extension which is required by WordPress.

Go to php.ini in cpanel File Manager

go to web root files and create new File phpinfo.php

<?php
phpinfo();
?>
add this code.

go to yourwebsite.com/phpinfo.php get current extension urls and change to 

match entention url same with php.ini
image

See loaded configuration file location

Go To Edit mode php.ini

; Directory in which the loadable extensions (modules) reside.
extension_dir = “/usr/local/lib/php/extensions”

edit directory like this in php.ini