Get iPXE to get results from web page

[sebastian]

One thing you can do, is to have your PHP script Query the lease table of the DHCP server and use that information to decide which iPXE script you want to boot. Then every computer boot the same iPXE script (http://server.com/boot.ipxe) - that is then linked to like (http://server.com/cgi-bin/ipxe.php), this script queries the lease table of the IP who did the request ($_SERVER['REMOTE_ADDR']), lookup MAC in ActiveDirectory, and then return a suitable iPXE script tailored for just that computer.

This means its also easy to implement access Control, so the web server can deny access to boot images that the computer in question are not allowed to boot according to iPXE script, preventing bypass of your system.

Such system would in fact pretty easy. Just use a suitable HTTP client module in PHP to automate requests to your router or switch web interface, to download the lease table.
If you have some sort of Telnet/SSH access, it would propably be easier to 'cat' the lease file directly from dhcpd run folder and parse that (using some Telnet/SSH library).
if security of the router/switch is Paramount even if "boot" web server is completely owned, you could set up a account in your router or switch that only have read-only access to the lease file and nothing else.
To avoid a Heavy load, you could cache records from the lease file into a local cache using their lease time as TTL.