Well first off every thing will be more expensive because we will have more money since we are not using it to buy food any more. we would get more money, save more money, and every thing will cost a lot more. Many people will lose jobs because they won't be making food any more (like people at mcdonalds) and then to get a job people will need higher intellect. The population of cows, pigs, and other animals that we eat will rise and they won't be domesticated any more (unless you want to keep a pet chicken, thats fine with me) and the evolution line might change. Then the downside is that the people live in a climate where it is mostly cloudy and dark will be more hungry and will probably move to warmer areas where they can get enough food. People in warmer climate can just sit outside for a few hours and they will be full and not hungry. As you can see if people began to use photosynthesis to get food. many things will change.
I hope this helped. :3