The front end is interacting with users. Most of the backend is a database with frame structure.

After determining the direction, start learning.

Beginners can learn along with online tutorials. (5 1 self-study network, rookie program, with detailed tutorials)

No problem, I don't understand this bug. I asked it on the forum (CSDN). Generally, you will get a reply, or you can discuss with them. I'm afraid not, I'm afraid not!

Knock the code more! Programming is no better than others, and you don't need to take too many notes. Remember the usage of important attributes clearly before writing more code. Big bosses are all piled up by code!