John Cena -- The Car Crash-termath [Photos]

John Cena's ride was the lead dog in a 3-way chain reaction crash in Philadelphia this morning ... and TMZ has the first photos from the smash site.

WWE.com broke the story ... Cena was leaving a media appearance ... when his SUV was rocked from behind by another car.

Now, we've learned ... Cena's ride was hit by a small Acura ... which was ALSO hit from behind by a massive big rig.