Murphy, who scored the winner at Morecambe last week in injury time, pounced with virtually the last kick of the game as the ball bobbled around the area and rifled it home to extend Stanley's unbeaten run to five games.
It had looked like Anthony Stewart had secured the points for the visitors. Defender Stewart got on the end of Josh Scowen's corner in the 72nd minute and his close-range shot went in off the inside of the post.
Wycombe created the better chances as Accrington needed on-loan Fulham goalkeeper Marcus Bettinelli to be at the top of his game.
From the resulting corner defender Kortney Hause should have done better but sent his free header wide.
Dean Morgan had a great chance to open the scoring after the break for the visitors when he rounded keeper Bettinelli, but the angle was too tight and he fired into the side netting.
James Gray then burst through at the other end with only Matt Ingram to beat but the keeper came out and denied him.
Bettinelli pulled off a strong double save to keep out Marvin McCoy and McClure at close range but then Wycombe made the breakthrough.
Piero Mingoia came close to a leveller for Stanley but Ingram pushed out his effort while Hause fired over at the death for Wanderers before Murphy's grandstand finish.