John Cena in Car Accident -- Ok to Fight The Rock at Wrestlemania

John Cena was involved in a car crash today -- the fomer WWE champ was rear-ended by a tractor trailer, but we're told he's ok and his epic upcoming fight with The Rock is not in jeopardy.

Cena was traveling in an SUV in Philadelphia when he was hit. We're told he is going to get checked out but right now it doesn't seem he was injured ... although signs of whiplash often don't show up for a day or two.

Cena is set to face off with The Rock on April 1 -- and the match has become one of the most anticipated in wrestling history.