Forward Porter, 24, and defender Johnson, 21, both joined the club at the start of the season and have agreed extensions after helping secure a 10th-place finish in the National League.
"I'm delighted to have Daniel on board for next season, he's had a fantastic season," manager Neil Smith said.
"George has been brilliant in every position we've asked him to play, he gives 100% and deserves his new deal."
Alan Dunne, Jack Holland and Jordan Higgs are the other players to remain contracted to Bromley for the 2017-18 season, but Connor Dymond and Lee Minshull have left the club.
George Porter and Daniel Johnson have signed new contracts with Bromley.