They have two photographs, one of the van and one of the background. Very carefully with scissors they cut around the van, then using glue they stick the van onto the background. They photograph the new picture, and once the Kodak Express shop has processed the film and printed the picture, they scan the fake picture then upload it to the internet. Clearly, photograph #4 was on transparent film and someone accidentally stuck it on the wrong way round.
I really don't believe
@motacyclist 's nonsense about the Beach's door changing sides.