Sorry to bump this, but the script works perfectly fine. I'm posting this for people who want this thing to get to work but don't know how to.
This is a list of thing you'll need to remember when you're going to use this:
Copy paste the code from that gamemonitor thread
Put the code in a .php file with php tags around it
To actually get variables use the following: $data = mta_getServer("127.0.0.1","22003");
Now the type of information is probably not what you're used to, it's not a string nor an array, but it's a class.
Now this is the code you want: echo $data->players . "/" . $data->maxplayers;
Instead of players or maxplayers you can also use: gameshort (type of game (mta)), port, name (server name), map and public (0 = private, 1 = public).
There's also something called rules, this is an array with stuff like the name of the gamemode and the version, so to get the gamemode name out of "rules" use: $data->rules["game"]; Note the quotes around game!
For a full overview of what the query returns use:
print_r($x);