From experience, at least the people around me, the PHD can get CAF in the first two years if they also did master in France. Since I did my master in France I can get CAF during my PHD. For example, I did master between 2010-2012 and I started my phd from 2013. In 2013, they calculated my CAF based on the situation of 2011 when we do not have any income. So we get enough help from CAF. Even now in 2015 we still get help from CAF but it is not as much as before. It is based on our situation (tax declaration) of 2013 . I did not tell any lie and I am salary instead of student.