A program called phi builder can be downloaded at the link, if your object has groups with the standard poser names you can load it into phi builder and it will automatically make the phi file for you.

http://www.royriggs.com/poser.html

objFile :Runtime:Libraries:character:new figures:testguy.obj
1 hip yxz
 2 abdomen yxz
  3 chest xyz
  3 head xyz
  3 lCollar xyz
  3 leftEye xyz
  3 lFoot xyz
   4 lForeArm xyz
  3 lHand xyz
 2 lShin xyz
  3 lShldr xyz
  3 lThumb1 xyz
   4 lThumb2 xyz
    5 lThumb3 xyz
  3 lToe xyz
  3 neck xyz
  3 rCollar xyz
  3 rFoot xyz
   4 rForeArm xyz
  3 rHand xyz
  3 rightEye xyz
 2 rShin xyz
  3 rShldr xyz
  3 rThumb1 xyz
   4 rThumb2 xyz
    5 rThumb3 xyz
  3 rToe xyz

Above is an actual phi file, it has the hierarchy information, the name of the figure part and then the rotation order for the body parts.