[amcrouch]

To me the senior title should be applied depending on the way you approach your role and not how you code.

As others have mentioned as a senior you can be left to implement changes without guidance, you will clean up issues as you come across them instead of leaving it to others, you suggest improvements, you make time to mentor and guide more junior members of the team, you know how to relate to muggles and you act like a team captain.

Knowing lots of different hosting environments and languages comes with experience. The approach you take to your role show's your all rounded skill set.