The 24-year-old midfielder is well known in Bad Canstatt, having played for VfB as a youth between 2010 and 2014.
Förster helped the VfB U-17s reach the final of the German championship back in the summer of 2012. After that, he went on to play for SV Waldhof Mannheim and 1. FC Nürnberg before joining SV Sandhausen in 2017, for whom he made 65 appearances in Bundesliga 2, scoring ten goals from midfield.
VfB sporting director Sven Mislintat: "In Philipp, we’re delighted to have brought a player back to VfB who had spent part of his youth development with us and who also came through the VfB academy. We’re getting someone who is young and hungry, physically very strong and also a very talented midfielder who will help us in our aim to get promotion back to the top flight."