在保留域名的同时重定向到移动版本

I have a site, I need to use JavaScript or some other method to redirect users to the mobile version (which has files on a specific directory). I created a subdomain (m.domain.com) but then I realised I do not have a wildcard certificate for the domain.com. Is there a way to redirect to the mobile version (i.e. change the home directory to the mobile directory) without affecting the domain name?

i.e. if I visit site domain.com from desktop, it loads from /var/www/html but if I visit from mobile, it loads from /var/www/html/mobile while retaining domain.com. I'm on apache ubuntu running PHP so I don't mind if this redirection is server-side.

Thanks in anticipation.

You can use a library to detect if the user is using mobile or desktop and then in your main folder :

/var/www/html

Add this index.php :

<?php

if(on mobile)
{
 include(mobile/index.php);
}
else
{
 // the code for desktop
}