FIX: your php installation appears to be missing the mysql extension which is required by wordpress.
Overview of the Problem
The problem is usually related to outdated php code, so you are maybe using the current php version, but your wordpress templates might not work with that version; usually it's the outdated MySQL plugin that has been removed in version 7.0. So you need to activate the plugin.
Hostitor provides all the latest versions of php, and you can select the php version from Hostitor Control Panel.
Check the php version of the WordPress template. It can found in the phpinfo.php file, or it is most likely to mention in any php file of the template.
Now make sure that the server is running the same version of php as your WordPress template.
If you're still finding the error -
then it may be due to the MySQL plugin. You need to activate the mysqli and/or mysqlnd and/or pdo_mysql. All those plugins come activated with Hostitor, and you don't need to worry about any of those.
Your php installation appears to be missing the mysql extension which is required by wordpress in Ubuntu or Debian VPS.
1. Connect to the server using SSH and check the php version you're using. Make sure that the WordPress template and Server is using the same php version. Check the version using
If it's not the same downgrade the php version or install a newer version of the WordPress template using FTP.
2. Update the required packages in your Ubuntu or Debian server.
3. Restart the server.
Are you still facing 'your php installation appears to be missing the mysql extension which is required by wordpress' with Hostitor? Please create a support ticket.