Brighton have completed the transfer of Israeli midfielder Beram Kayal from Celtic following a work permit hearing.
Nicolas Anelka is free to resume his career in England after completing an education course following his quenelle gesture.
The 27-year-old, who moved to the Rotterdam-based side from ADO Den Haag in 2012, will now remain at De Kuip until at least the summer of 2017.
"I feel a lot of appreciation from the club, which is an important reason for me to stay at Feyenoord longer," Immers told the club's official website, feyenoord.nl.
"I'm really really enjoying myself and I feel completely at my place at Feyenoord. For me that was one of the conditions to stay here longer.
"I'll go on holiday first but I'm already looking forward to the first practice and the qualifying rounds of the Champions League."