AoOs against the same enemy on his turn?

Question

I have seen this question for D&D 4e: Attacks of Opportunity from moving within a threatened area? and I was wondering about attacks of opportunity in Pathfinder/3.5e.

If an enemy goes from one threatened square to another one threatened by the same guy twice, and the threatening creature has combat reflexes and enough dexterity, could he be making more than one AoO against the same enemy for that movement?

As an example, imagine that a Medium size creature (A) with 5ft. reach charges against a Large humanoid with a reach weapon and a non-reach natural attack (e.g. a bite), Dex 20 and Combat Reflexes (B).

B threatens from 20ft to 10ft with his reach weapon and from 10ft to 5ft with the bite. For a total of 4 squares threatened on a straight line.

So, does A provoke three AoOs from B whenever he charges, for leaving 20ft., 15ft. and 10ft. during the same move?

Further, lets say B gets Hold the Line feat, which states:

Benefit

You may make an attack of opportunity against a charging opponent who enters an area you threaten. Your attack of opportunity happens immediately before the charge attack is resolved.

Does A now provoke an AoO from B for both entering and leaving these squares, for a total of 6?

Answer 1

Sorry, one movement only provokes one AoO from a given defender.

See the d20pfsrd:

If you have the Combat Reflexes feat, you can add your Dexterity modifier to the number of attacks of opportunity you can make in a round. This feat does not let you make more than one attack for a given opportunity, but if the same opponent provokes two attacks of opportunity from you, you could make two separate attacks of opportunity (since each one represents a different opportunity). Moving out of more than one square threatened by the same opponent in the same round doesn't count as more than one opportunity for that opponent. All these attacks are at your full normal attack bonus.

So if you shriek "SERPENTINE!!!" and run circles around your opponent, they still only get one "leaving a threatened square" AoO on you.

The opportunity from Hold the Line is different, but only works once upon them entering your threatened area. So you would get only one from Hold the Line and one for them leaving a threatened square.

Note that the leaving a threatened square is per round - not even just per turn - with the Mythic rules in use in our WotR campaign we've been finding a lot of cases where you get to act multiple times in a round, even charge multiple times, etc. If by hook or crook someone charged you, ran off, charged you again, and ran off again over the course of a round (on their turn or across multiple turns), you would still only get 1 AoO for them leaving your threat but could get multiple from Hold the Line, if they actually leave and enter your threatened area with a charge twice. Up to the limit of the number of AoOs you have.

Answer 2

Does A now provoke an AoO from B for both entering and leaving these squares, for a total of 6?

No, just 2 attacks are provoked.

Since from Attacks of Opportunity

Moving out of more than one square threatened by the same opponent in the same round doesn’t count as more than one opportunity for that opponent.

The opponent can only ever provoke one attack of opportunity from the same opponent for moving out of a threatened square. Even encircling an opponent, or moving in and out of their threatened squares only counts as one opportunity, provided the movement that provokes is in the same round.

The opponent can provoke more than once though, as explained in the section on Combat Reflexes,

If you have the Combat Reflexes feat you can add your Dexterity modifier to the number of attacks of opportunity you can make in a round. This feat does not let you make more than one attack for a given opportunity, but if the same opponent provokes two attacks of opportunity from you, you could make two separate attacks of opportunity (since each one represents a different opportunity). Moving out of more than one square threatened by the same opponent in the same round doesn’t count as more than one opportunity for that opponent. All these attacks are at your full normal attack bonus.

Hold the Line, presents a different opportunity.

You may make an attack of opportunity against a charging opponent who enters an area you threaten

Even though moving out of a threatened square can only provoke once, the feat grants a new opportunity for entering an area you threaten. Since an opponent can only enter an area you threaten once during a charge, this can only add one opportunity.

If you are wielding a reach weapon and have the Hold the Line feat, a charging opponent provokes when they enter the "area you threaten", thus you would need to make the attack of opportunity with a weapon that has reach.

Strictly speaking, this would not work because attacks of opportunity are resolved just before the action that triggers them, thus the opponent would still be out of reach at the time you make your attack. However, the feat adds this text,

Your attack of opportunity happens immediately before the charge attack is resolved.

The rules don't come out and say you must make the attack with the weapon that threatens, but they do say

An attack of opportunity is a single melee attack

So unless you have another reach weapon, you would need to make the attack with that weapon.

With the second opportunity, provoked by moving out of a threatened square, since an attack of opportunity

interrupts the flow of actions,

the target has not yet left the square, so by the same reasoning, you must also take this attack with the reach weapon.

Thus, to summarize, you would gain one attack of opportunity when the opponent enters an area you threaten from Hold the Line and one attack of opportunity when the opponent starts to exit that same square. Both attacks would need to be with a (melee) reach weapon.