Get The Uploaded Files

You may access uploaded files using the getUploadedFiles() method on the request object like so:

// get all uploaded files
$files = $request->getUploadedFiles();

This returns an array of \Psr\Http\Message\UploadedFileInterface keyed by the name of the <input /> element.

Handling Uploads

Let's suppose we have a very simple upload form like so:

<!-- make sure the attribute enctype is set to multipart/form-data -->
<form method="POST" action="/upload" enctype="multipart/form-data">
	<input type="file" name="uploaded_file" />
	<input type="submit" />
</form>

Since the form action attribute points to the '/upload' endpoint, we will have to write a route that handle's the upload route like so:

$app->post('/upload', function($request, $response, $next) {
    $files = $request->getUploadedFiles();

    $uploaded_file = $files['uploaded_file'];
});

Multiple Files Upload:

To upload multiple files, we will have to add the multiple attribute to our upload field along with appending [] to the name field like so:

<form method="POST" action="/upload" enctype="multipart/form-data">
	<input type="file" name="uploaded_files[]" multiple />
	<input type="submit" />
</form>

Alternatively, you could also create any number of distinct file upload fields with the same name followed by [] like so:

<input type="file" name="uploaded_files[]" />
<input type="file" name="uploaded_files[]" />
<!-- ... -->

Next, we can handle multiple uploaded files like so:

$app->post('/upload', function($request, $response, $next) {
    $files = $request->getUploadedFiles();

    // handle multiple inputs with the same key
    foreach ($files['uploaded_files'] as $uploadedFile) {
        if ($uploadedFile->getError() === \UPLOAD_ERR_OK) {
            // do something...
        }
    }
});

Validating Uploaded Files

Consider, for example, uploading images:

$pictures = $req->getUploadedFiles();
    
foreach ($pictures['uploaded_files'] as $picture) {
    // was there an error uploading?
    if (($err = $picture->getError()) !== \UPLOAD_ERR_OK) {
        throw new \Exception("There was an error `$err` while uploading picture(s)!");
    }
    // is the image size greater than 5mb (5242880 bytes)?
    else if ($picture->getSize() > 5242880) {
        throw new \RuntimeException('File size limit exceeded!');
    }
    // is the image in an unacceptable format?
    else if (! in_array(
        exif_imagetype($picture->getStream()->getMetadata('uri')), 
        [IMAGETYPE_PNG, IMAGETYPE_JPEG, IMAGETYPE_GIF]
    )) {
        throw new \Exception("Sorry, but the selected image format is not allowed!");
    }
}

Moving Uploaded Files

The \Psr\Http\Message\UploadedFileInterface supports some useful methods to work on the uploaded files. We could use these methods to move the uploaded file to a new directory like so:

$files = $request->getUploadedFiles();
// assuming single file is uploaded with the key 'uploaded_file'
$uploadedFile = $files['uploaded_file'];

// create encoded file name
$extension = pathinfo($uploadedFile->getClientFilename(), PATHINFO_EXTENSION);
$basename = bin2hex(random_bytes(8));
$filename = sprintf('%s.%0.8s', $basename, $extension);

$directory = __DIR__ . '/uploads';

$uploadedFile->moveTo($directory . DIRECTORY_SEPARATOR . $filename);