How to validate $_FILES using Respect Validation library

I'm using Respect Validation to attempt to validate a file upload. The problem I'm having is the validation always fails, even though the correct image has been uploaded.

Here's my code:

public function updateProfilePicture(Request $request, Response $response, $args = []) {

    $files = $request->getUploadedFiles();

    if(empty($files['image'])) {
        throw new AppException('Invalid image');
    }

    // Validate image
    $validator = v::key('image', v::image());

    try {
        $validator->assert($files);
        // $validator->assert($_FILES);
    } catch(NestedValidationException $e) {
        throw new AppException($e->getMessage());
    }
}

The error I'm getting is:

{
  "status": false,
  "data": null,
  "message": "All of the required rules must pass for { \"image\": { \"name\": \"twitter.png\", \"type\": \"image/png\", \"tmp_name\": \"/private/var/folders/ry/kgy3g6v96s71jg3htn6r5rt80000gn/T/php7x3P6w\", \"error\": 0, \"size\": 210955 } }"
}

As suggested in the comments I tried using $validator->assert($files['image']);. This didn't work and yields the following error:

{
  "status": false,
  "data": null,
  "message": "All of the required rules must pass for `[object] (Slim\\Http\\UploadedFile: { \"file\": \"/private/var/folders/ry/kgy3g6v96s71jg3htn6r5rt80000gn/T/phppJn1Uw\" })`"
}

The $files variable contains:

array(1) {
  ["image"]=>
  object(Slim\Http\UploadedFile)#120 (8) {
    ["file"]=>
    string(66) "/private/var/folders/ry/kgy3g6v96s71jg3htn6r5rt80000gn/T/php8sPpkD"
    ["name":protected]=>
    string(11) "twitter.png"
    ["type":protected]=>
    string(9) "image/png"
    ["size":protected]=>
    int(210955)
    ["error":protected]=>
    int(0)
    ["sapi":protected]=>
    bool(true)
    ["stream":protected]=>
    NULL
    ["moved":protected]=>
    bool(false)
  }
}

And $_FILES contains:

array(1) {
  ["image"]=>
  array(5) {
    ["name"]=>
    string(11) "twitter.png"
    ["type"]=>
    string(9) "image/png"
    ["tmp_name"]=>
    string(66) "/private/var/folders/ry/kgy3g6v96s71jg3htn6r5rt80000gn/T/phpm0Gv35"
    ["error"]=>
    int(0)
    ["size"]=>
    int(210955)
  }
}

As suggested in the comment I've tried $validator->assert($_FILES['image']['tmp_name']); and get the following error:

{
  "status": false,
  "data": null,
  "message": "All of the required rules must pass for \"/private/var/folders/ry/kgy3g6v96s71jg3htn6r5rt80000gn/T/php8E5apg\""
}

I've tried to Google to see how others are doing it but was unable to find anything useful.

Solution

Try to do this:

var_dump(v::image()->validate($_FILES['image']['tmp_name‌']‌));