exposing attachment uploading to the front end — delicate

here is the function i use whenever i accept uploads from front end and you can use it in your template files:

function insert_attachment($file_handler,$post_id,$setthumb='false') {

  // check to make sure its a successful upload
  if ($_FILES[$file_handler]['error'] !== UPLOAD_ERR_OK) __return_false();

  require_once(ABSPATH . "wp-admin" . '/includes/image.php');
  require_once(ABSPATH . "wp-admin" . '/includes/file.php');
  require_once(ABSPATH . "wp-admin" . '/includes/media.php');

  $attach_id = media_handle_upload( $file_handler, $post_id );

  if ($setthumb) update_post_meta($post_id,'_thumbnail_id',$attach_id);
  return $attach_id;
}

Usage:

// set $post_id to the id of the post you want to attach
// these uploads to (or 'null' to just handle the uploads
// without attaching to a post)

if ($_FILES) {
  foreach ($_FILES as $file => $array) {
    $newupload = insert_attachment($file,$post_id);
    // $newupload returns the attachment id of the file that
    // was just uploaded. Do whatever you want with that now.
  }
}