When a charging Bull elephant comes at you, running means death, so you are supposed to hold your ground.
Adam Rifkin stashed this in Elephants!
Comment from Redditor drunk-scientist:
In this case, the elephants ears were fanned out, indicative of a mock charge. If they were against it's body, well, it might have been a different story. Source: 5 seconds of googling
According to that article, standing still is your best option though, as most charges are 'mock charges'. Showing your back or running away encourages the elephant to give chase, and they will probably win. Biologist Michael Fahey says that "the probability of you getting killed is much lower if you stand your ground than if you run."
If you do end up running, though, run in a zig-zag way likely to confuse the elephant, climb a tree, hop in a ditch, throw an item of clothing as a decoy or play dead.