The 24-year-old is relieved to have some security: "It's very pleasing to have my future sorted," Ephraim told the club's official website.
"There's been a lot of player movement - both in and out - so I'm happy that I've signed and I know where my future lies.
"The manager has been very good to me ever since he arrived here. He backed me up with a new contract last year and now another one this season.
"Now I'm looking forward to try to force my way into the 25-man squad and stake a claim for a place in the team."