In C function swe_cotrans we allow for a 3-dimensional position vector which includes distance. That is fir the prigrammer's convenience. Distance is never changed in a rotational coordination transfirmation.
in the php implementation there are no vectors, but separate parameters lng, lat, dist in input and return.
I suggest to drop dist from the parameter list, and from the return array.
Alois:
Don't forget to update the inline documentation.