Can't send file as form data using cURL

Question

I am trying to send a cURL request via the command line. Below is my request

curl -i http://localhost/test/index.php 
-X POST 
-F "name=file.png" 
-F "content=@/var/www/html/test/file.png"

The problem I'm having is that the file isn't getting sent with the request. The name is getting sent fine but not the file. Can anyone see if I am doing anything obviously wrong?

I've check the permission on the file as I thought that might be the problem but they are fine

The backend is written using the PHP Slim framework and I'm doing the following $app->request->post('content');

Answer 1

If you want to be able to access the file's contents using $app->request->post('content');, your curl request must use a < instead of an @ for the content field,

curl -i http://localhost/test/index.php -X POST -F "name=file.png" \
  -F "content=</var/www/html/test/file.png"

From curl's manpage:

To force the 'content' part to be a file, prefix the file name with an @ sign. To just get the content part from a file, prefix the file name with the symbol <. The difference between @ and < is then that @ makes a file get attached in the post as a file upload, while the < makes a text field and just get the contents for that text field from a file.

By using @, you marked the field as a file. Technically, this adds a Content-Disposition header to the field (RFC 2388, if you're interested). PHP detects that and automatically stores the field inside $_FILES instead of $_POST, as Raphaël Malié remarked in a comment, which is why you can't access the contents using $app->request->post.

You should consider to switch to using $_FILES in your backend, though, if you want to support uploading using browsers' <input type=file> elements and forms. Those always set a Content-Disposition header.