Best way to control phalanxes is not to control them. Basically tell them to march straight forward until they hit the enemy. If you target a unit with them they sometimes seem to turn too much causing their pikes to be lifted too often. Of course remember to halt them if the enemy get's too intermingled with them. And when you have a whole line of phalanxes march them together and when 1 unit hits an enemy halt them all, this way your phalanx line only has 2 flanks exposed.