Php upload file yields error code 4. Why?

Other solution (PHP 7.3.11)

for answer @Weblurk https://stackoverflow.com/a/21698740/9635711

Don't works:

<input id="files" multiple="true" name="file_images_send[header_image]" type="file">
<input id="files" multiple="true" name="file_images_send[header_image]" type="file">

It works - Solution - with array "[]" end name input

<input id="files" multiple="true" name="file_images_send[header_image][]" type="file">
<input id="files" multiple="true" name="file_images_send[header_image][]" type="file">

In this case, the problem was: I had multiple input elements with the attribute name="image". When I changed to individual names the error disappeared.