php - When uploading files asynchronously, why is tp5 $request->file(); unable to get the value?

Question

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!

Answer 1

$_FILES contains a value, that means there is a problem with the file method of tp.
Look at the source code of the file method and trace it.