Skills, weapon or class?

[Cubical]

What would be the best way to save your skills? In a weapon or class, I'm leaning twords class because I could use them without having to remake them for monsters.

Also I was wondering what would be the best way to call it if it were in a class?
weapon

PHP Code:

public function triggerSkill(skillname){
  join(skillname);
  onUseSkill("npc");
} 


class

PHP Code:

public function onUseSkill(attacker){
  //do stuff
} 


or would there be a better way to do it?