What is if you accidentally like a photo on facebook and then unlike it?

If you accidentally like a photo on Facebook and then unlike it immediately, the person who posted the photo will not receive a notification of your like. However, if they have push notifications turned on, they may see a brief notification pop up on their phone before it disappears. Additionally, if they happen to see the like notification on their own before you unlike it, they may still be able to see that you liked it for a brief period of time in the activity log. But as soon as you unlike it, the like will disappear from both their notification and the activity log, and they will not be able to see that you liked their photo.