File Upload visible in $_FILES but drupal file functions create empty file

Question

I created a custom form with a file upload field:

$form['csvfile'] = array(
    '#title' => 'CSV File',
    '#type' => 'file',
);

When I submit the form, I can see the correct information in the $_FILES array:

However, when I try to use the code in the examples module to get the contents of that file and write it to an unmanaged file, the file is empty.

So, the resulting file is 0 bytes long.

How do I access the uploaded file in a drupal-y way? I know I can just use the basic PHP functions to access the file, but I'm trying to learn how to do it the way drupal intends.

My submit handler code is almost entirely lifted from the examples module.

function herdapi_form_bulkupload($form, &$form_state) {
    $form = array();
    $form['email'] = array(
        '#title' => 'Owner Email',
        '#type' => 'textfield',
    );

    $form['password'] = array(
        '#title' => 'Password',
        '#type' => 'password',
    );

    $form['csvfile'] = array(
        '#title' => 'CSV File',
        '#type' => 'file',
    );

    $form['submit'] = array(
        '#value' => 'Upload',
        '#type' => 'submit',
    );

    $form_state['rebuild'] = TRUE;
    $form_state['redirect'] = FALSE;

    return $form;
}

function mymodule_form_bulkupload_submit($form, &$form_state) {

    dsm($form_state);
    dsm($_FILES);
    $data = $form_state['values']['csvfile'];

    // With the unmanaged file we just get a filename back.
    $filename = file_unmanaged_save_data($data, NULL, FILE_EXISTS_REPLACE);
    if ($filename) {
        $url = file_create_url($filename);
        $_SESSION['file_example_default_file'] = $filename;
        drupal_set_message(
            t('Saved file as %filename (accessible via !url, uri=<span id="uri">@uri</span>)',
                array(
                    '%filename' => $filename,
                    '@uri' => $filename,
                    '!url' => l(t('this URL'), $url),
                )
            )
        );
    }
    else {
        drupal_set_message(t('Failed to save the file'), 'error');
    }
}

Answer 1

Drupal forms which include a file upload field must also set the encoding type to multipart/form-data.

  $form['#attributes']['enctype'] = 'multipart/form-data';

Reference: Drupal.org: Uploading Files

---

There is a good checklist for debugging your situation here:

https://stackoverflow.com/questions/3586919/why-would-files-be-empty-when-uploading-files-to-php

Not mentioned in the checklist there is that Suhosin, a commonly installed extension, can empty some submitted values. As well as following the checklist in the linked question, check to see if you have Suhosin installed - if so then you may be

One thing I'd try straight away is whether uploading a very small file triggers this bug. If so that might suggest that you're hitting a limit in PHP's max post data or Suhosin.

Answer 2

Even though this is an old question, it is among the first results when looking for this matter using Google. The answer is found in https://www.drupal.org/node/1537950 from where I modify a little the original code:

function mymodule_form_bulkupload_validate($form, &$form_state) {
  $file = file_save_upload('csvfile', array(
    'file_validate_extensions' => array('csv'),
  ));
  if (!$file) {
    form_set_error('csvfile', 'No file was uploaded');
  }
  $form_state['values']['file'] = $file;
}

Long story short, since this isn't a managed_file, Drupal doesn't do anything more than just add the "multipart/form-data" to the enctype attribute of the form. Anything more, like saving locally the $_FILES, validating and adding the $file to the $form_state array is something you are responsible for.