1. When I use fileinput for asynchronous upload, I submit it to the background through routing.

2.Routing

3.Background reception

4. Problem
Return [1,{}]
Cannot get the value
5.1 Supplement
If you use $_FILES['cover']; here, you can get the value
5.2 Supplement
If the form is submitted, the value can be obtained
6. Please clarify the confusion! Grateful!