EllisLab/CodeIgniter — comment on commit d72973519623f40f121e9cd2df93146ee2543a1f
File: system/core/Loader.php line 905
By philsturgeon:

Only needs it once. You'll notice that `$last_slash` was being used as `X + 1` in both locations. It is not incremented in the first instance and so no more maths has to be done to +1 again.