isset and !empty not passing through a check for uploaded files

问题

I have an upload form with a file to be uploaded. The issue I have is that even when no file is uploaded the if(isset($_FILES)) OR if(!empty($_FILES)) still passes as successful:

$_FILES = $HTTP_POST_FILES;
if($_POST['type'] == 'photo' && isset($_FILES)){
// returns true even if no file is uploaded. What am I missing!
}

回答1:

Being a superglobal, $_FILES is presumably always set, regardless whether an uploaded file exists or not.

Check for the file upload(s) you would expect and look at the size field. (Apparently according to the User Contributed Notes in the manual, if the form contains the upload element, it is possible that even isset($_FILES["my_file_name"]) will return true even though there was no file selected.

This should work reliably:

if($_POST['type'] == 'photo' && 
   ((isset($_FILES["my_file_name"]["size"]) && 
    ($_FILES["my_file_name"]["size"] > 0)) ){

(the isset() is to prevent a "undefined index" notice.)

What do you do this for, by the way?:

$_FILES = $HTTP_POST_FILES;

来源：https://stackoverflow.com/questions/2549055/isset-and-empty-not-passing-through-a-check-for-uploaded-files