Domain re-pointing through PHP... ?

I have to get re-pointed a domain like what i explained in the image by using PHP.

 

DNS level redirection is not possible with PHP. If you only want to redirect HTTP traffic then go for this:

<?php

    // however you determine what server to redirect to
    $server = 'host1';

    switch ($server) {
        case 'host1':
            header("Location: http://www.host1.comn.us/");
            break;
        case 'host2':
            header("Location: http://www.host2.comn.us/");
            break;
        case 'host3':
            header("Location: http://www.host3.comn.us/");
            break;
    }

    exit;
?>

PHP:

 

If the DNS level redirection is not possible in PHP, then how i can do this ?
Is there any other way to get this done???