How do get Client MAC Address or Computer Name through PHP or in Javascript?

Actually I want to restrict my web application to open on specific system(s) only for few systems/users. If client machine mac address matches to my assigned machine mac address which is i have, Eg. if (default_mac == client_mac_address) { // then Login } else { // Redirect to home page or error page}

Or is there any other way to restrict the web application to other users.

Please help me. Thanks in advance..