Halfar began his career at MFC Phönix Mannheim 02. In 1997, he joined 1. FC Kaiserslautern. He gave his debut on 11 December 2005 against Bayern Munich. His first two goals Halfar scored in the match MSV Duisburg – 1. FC Kaiserslautern, with those goals he is the youngest player of Kaiserslautern ever to score (18 years, 28 days). Since this season, Halfar has been seen as a very big talent. In August 2007 he moved to Arminia Bielefeld. He scored his first goal for his new club on 22 November 2008 against VfB Stuttgart. After three seasons with Arminia Bielefeld and scoring only one goal for the club, he was sold on a free transfer to TSV 1860 München. In the summer of 2013 he transferred to 1. FC Köln, signing a three-year contract.