rename attachments based on parent-post-title on upload

Question

I know there a some functions already avaible here for this task, but none of them seem to work as needed.

The best way seems to me adding a filter to wp_handle_upload_prefilter like kaiser does in this example. Unfortunately the file only gets the parent-post-title if the post is already saved to the database.

---

Another approach is to add a function to add_attachment like Ijaas does here. Then the file gets the parent-post-title as name, but no thumbnails are created. And my attempt in using wp_generate_attachment_metadata(); to create the missing image sizes, ended in an endless loop (propably cause I'm using it the wrong way, but now I'm a bit scared by this function).

---

Would be great if there was a way to pass the title to wp_handle_upload_prefilter even if the post isn't saved yet.

Oh by the way, this is my endless function, maybe somebody can tell me what's wrong with it. DON'T USE THIS FUNCTION !!!

add_action('add_attachment', 'fkp_rename_attacment');
function fkp_rename_attacment($post_ID){

  $post = get_post($post_ID);
  $file = get_attached_file($post_ID);
  $path = pathinfo($file);
  $parent = get_post($post->post_parent);
  $p_author = get_the_author_meta( 'display_name', $parent->post_author );
  $p_author_san = sanitize_title($p_author);

  $newfilename = $parent->post_name . '-' . $p_author_san . '-' . $post_ID;
  $newfile = $path['dirname']."/".$newfilename.".".$path['extension'];

  rename($file, $newfile);    

  $wp_filetype = wp_check_filetype(basename($newfile), null );
  $wp_upload_dir = wp_upload_dir();
  $attachment = array(
    'guid' => $wp_upload_dir['url'] . '/' . basename( $newfile ), 
    'post_mime_type' => $wp_filetype['type'],
    'post_title' => preg_replace('/\.[^.]+$/', '', basename($newfile)),
    'post_content' => '',
    'post_status' => 'inherit'
   );
  $attach_id = wp_insert_attachment( $attachment, $newfile, $parent->ID );
  require_once(ABSPATH . 'wp-admin/includes/image.php');
  $attach_data = wp_generate_attachment_metadata( $attach_id, $newfile );
  wp_update_attachment_metadata( $attach_id, $attach_data );
}

DON'T USE THIS FUNCTION !!!

Answer 1

After trying to add a function to publish_post and creating a lot of unnecessary files I tried to blemish kaisers function to fit my needs.

function modify_uploaded_file_names( $image ) {
    // Use part of the post or user object to rename the image
    get_currentuserinfo();
    global $post, $current_user;

    // only do this if we got the post id, 
    // otherwise they're probably in the media section 
    // rather than uploading an image from a post
    if ( isset( $_REQUEST['post_id'] ) ) {
        // get the ID
        $post_id  = absint( $_REQUEST['post_id'] );

        // get the post OBJECT
        $post_obj  = get_post( $post_id );

        // get the post slug
        $post_slug = sanitize_title($post_obj->post_title); 

        // get the author
        $author = sanitize_title( get_the_author_meta( 'display_name', $post_obj->post_author ) );

        switch( $image['type'] ) {
            case 'image/jpeg' :
                $suffix = 'jpg';
                break;

            case 'image/png' :
                $suffix = 'png';
                break;

            case 'image/gif' :
                $suffix = 'gif';
                break;
        }

        // if we found a slug
        if ( $post_slug ) 
            $image['name'] = "{$author}-{$post_slug}-{$random_number}.{$suffix}";
    }
    else {
        $image_name    = str_place( ' ', '-', strtolower( $current_user->data->user_nicename ) );
        $image['name'] = $image_name . '-' . $file['name'];
    }

    return $image;
}

// Only one arg, so 4th attr not needed - Priority set to later 20
add_filter( 'wp_handle_upload_prefilter', 'my_modify_uploaded_file_names', 20 );

There are only some small changes

1. replaced $post_obj->post_name with sanitize_title($post_obj->post_title) since post_name only was present in my tests when the post already was saved.
2. deleted the random-numbers, cause wp_handle_upload uses wp_unique_filename() anyway.
3. Added the author-name to the file-name, but that's just something I need.