This code definitely needs to be smarter. First, put all your server names in an indexed array, that is by the number. I just write the code, OK.
in the post part of your php put $svr = $_POST['server_name'];
make all the values in the options just numbers, no need for the quotes, and add one more number than the number of servers for the 'all' option, in this case 2.
remember that php numbers from 0
if ( $svr != 2 ) $name = $server_names[$svr];
// In here you put a for loop that prints out all the server names from $server_names