Record a weird picture upload problem

Today, when I was writing the form submission , Find a strange problem , I wonder .

Currently working on a mall module , When I want to upload pictures of the front and back of my ID card and the business license of the merchant , One upload will be successful , An upload failed , Then one succeeded again , One failed again . I can't figure it out , What the hell is this ？

Then double check my code , I didn't find anything wrong , For a long time , Later, I found another one on the Internet and said , Add a random number parameter or current time parameter , Then I tried , It's really good . Think carefully , It may be that multiple uploads make the server think it is a duplicate request , And then send a request to No .

In fact, when sending a request , Just add a parameter equal to a random number or a parameter of the current time after the link , In order to distinguish between , Every request is different , So you can upload it easily . Off duty ！