"Philipp is still young but has gained great experience from playing in the Bundesliga with Borussia Dortmund and on the international stage with Switzerland. He also played in the Champions League during his time with Basel and so is used to top level football," said the Liverpool boss.
"He is an offensive player with great energy and a winning mentality. His strength is going forward and I am confident he will be prove to be a quality addition to our squad."