A vincenty formula to calculate length would be nice

I made some code to calculate length with the vincenty formula, and now I saw geoPHP is missing it, so I added it to LineString.class.php It is basically the same as on the movable type website. I copied the beginning of the greatCircleLength function to the beginning of it, so it should be working. The original I used was working anyway. I havent tested this modified version, but since it is basically copy and paste, it should be working. (I hardly manage to get things right the first time, so check it). If it is fine, just add it to the other classes that need it.