php - WeChat verification server validity bug

Question

According to this flow chart, my server will receive echostr and return it directly to WeChat. There is no need to do the following hash verification. The field received by the WeChat server can also be verified, because if it succeeds, it will also return this to the WeChat server. Then I will Why not just return i? I'm new to this trap, I hope you can forgive me

Answer 1

Because data is very likely to be tampered with during transmission, the data must be verified