He was scheduled to be a free agent following the season.
Jernigan, 25, was signed to a one-year deal by the Eagles this offseason and has fit in perfectly in Philadelphia.
With Cox and Jernigan in the fold, the Eagles are investing plenty of money in their defensive line. The Eagles acquired him from the Ravens in early April.
Fewer chances on third down mean fewer sacks. Paired with Pro Bowler Fletcher Cox in the Eagles' trenches, where Philadelphia ranks No. 1 in run defense, the former Baltimore Ravens draft pick has logged 17 tackles and 1.5 sacks through nine games, although a handful of his tackles have also come behind the line of scrimmage.
Saudi-led coalition reopens Yemen's Aden and Seiyoun airports
The action led the coalition to impose all-out blockade and closed all air, sea and land ports of Yemen for fears of smuggling weapons to the rebels.
Jernigan is now signed through the 2021 season.
More important than the numbers, though, is that he has helped solidify an Eagles pass rush that is one of the more formidable ones in the league. "We stuck with him", Eagles defensive coordinator Jim Schwartz told reporters.
Jernigan's contract is worth a total of $48 million that includes $26 million fully guaranteed, as first reported by ESPN's Adam Schefter. Cox, another great run defender, missed two games and much of a third game, but the Eagles' defense didn't miss a beat when Jernigan moved into Cox's three-technique position. If Jeffery, who hasn't had a 100-yard game yet for the Eagles, is seeking upward of $15 million per season, would vice president of football operations Howie Roseman have the funds - or desire - to make that happen? Last year, Baltimore started attacking a little bit more and I had my best year. That'll be a problem for the Cowboys, Redskins and Giants.