Sometimes, you want to work together with someone without making a formal alliance. The VGA Planets game has offered quite a number of ways to achieve that, and PHost supports and improves these.
Friendly Code Matching: When two objects have the same friendly code, they behave (roughly) as if they were allied. See Friendly Code Matching for details. The Universal Minefield Friendly Code helps you to coordinate movement of a large allied fleet through your minefields.
Giving away things: You can transfer cargo to foreign ships and planets. Some such cargo transfers can be done directly, some need a mission (Beam down credits, Transfer torpedoes, Transfer fighters, Transfer money) or friendly codes (bdm, btX, bum). You can give away ships using the gsX friendly code or the give command, the command also works for planets. More details can be found in the respective descriptions.
Sharing Information: No-one prevents you from telling others where your weak spots are (unless AllowPlayerMessages is off, of course). Some client programs include functions to transmit data to other players in a way that the receiver sees the information in his starchart.