Uploading a file to a cck file field using PHP and cURL

This tutorial explains how to upload a local file to a Drupal site using cURL.

Anonymous user upload:

1. Install filefield module.
2. Goto story content type 'Manage fields'(admin/content/node-type/story/fields).
3. Add a new file field to story content by the name field_file.
4. Grant anonymous users the permission to create a story content and to view/ edit field_file (admin/user/permissions).
5. Execute the following PHP (after changing the $file name):
   
   <?php
  global $base_url;
  $ch = curl_init();
  curl_setopt ($ch, CURLOPT_TIMEOUT, 60);
  curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
  curl_setopt($ch, CURLOPT_POST, 1); 
 
  $content_type = 'story';
  $url = "$base_url/node/add/$content_type";
  curl_setopt($ch, CURLOPT_URL, $url);
  $file = "";  // Enter the full path of your local file.
  $post_data = array(
    'title' => 'cURL title',
    'body' => 'cURL Body',
    'files[field_file_0]' => "@$file", // Always use the @ sign before the file name, when posting a file.
    'field_file[0][fid]' => 0, // This is required.
    'field_file[0][list]' => 1,  // This is required as well.
    'form_id' => $content_type .'_node_form',
    'op' => 'Save',
  );
  curl_setopt($ch, CURLOPT_POSTFIELDS, $post_data);
    
  $result = curl_exec($ch);
  $headers = curl_getinfo($ch);
  // We assume that if the url didn't change then the form submit failed. 
  if ($headers['url'] == $url) {
     drupal_set_message("Cannot add $content_type.");
  }
  else {
      drupal_set_message("$content_type content created.");
  }         
  curl_close ($ch);
?>

A new story node should have been created authored by anonymous user.

Note: a nice tip on how to figure Out What A POST Looks Like can be found under section 4.5.