Phillips opened the scoring after two minutes and then set-up James Morrison for the second as the Baggies took control of the first half.
However, Hull hit back with a tremendous strike from Richard Garcia and, following the dismissal of Paul Robinson 17 minutes from time, the Baggies finally wrapped up the points with a late break-away goal from Roman Bednar.
With their promotion rivals dropping points, West Brom knew a win would take them two points clear at the top of the table and they got off to the best possible start.
Ishmael Miller released Chris Brunt on the left and the winger's delivery found Phillips, who pushed the ball beyond Boaz Myhill.
Hull hit back with Dean Windass being thwarted by Dean Kiely and Ian Ashbee headed over Dean Marney's free-kick.
However, Hull were hit by a sucker punch after 32 minutes.
This time Phillips turned provider as he slipped a pass through to Morrison, who calmly tucked the ball into the bottom right corner from 12 yards.
With the game slipping away from Hull, manager Phil Brown brought on strikers Fraizer Campbell and Nick Barmby.
The changes nearly reaped immediate rewards when Barmby was denied by Kiely.
Hull did find a way back into the game 18 minutes from time when Garcia played a one-two with Sam Ricketts and cut infield from the right to curl home a brilliant led-footed shot into the top-left corner from 20 yards.
Seconds later, Hull were given added impetus when Robinson clattered into Campbell and was shown a second yellow card.
Hull piled on the territorial pressure thereafter but were failing to carve out clear chances, although Bryan Hughes volleyed over from 12 yards.
However, West Brom wrapped-up the points deep into stoppage time when Bednar raced clear on a counter attack and scored with a right-footed shot from 20 yards that squirmed under Myhill.