How can I add a default description to uploaded files?

Question

Is there a way to add a default description for media files as soon as they are uploaded to WordPress?

Specifically, I want to modify the code here to extract the text from PDF files and include it in the description for the media item in WP.

I've found that adding a filter using the "attachment_fields_to_save" hook will allow me to change the description (post_content) for media, but it only works after I click "update" on the Edit Media screen. When items are first uploaded, the description is empty by default.

Thanks for any help!

Answer 1

If we look at the source of wp_insert_attachment() we find the hooks edit_attachment and add_attachment. In your case we could use the add_attachment hook. The callback takes the attachment's ID as a parameter. By looking at the database table wp_posts we see that the description is saved as post_content and the caption as post_excerpt:

Then you could try this snippet:

/**
 * Default title, caption and description to uploaded attachments
 *
 * @param integer $post_ID The attachment's ID
 * @return void
 */

function wpse_121709_upload_defaults( $post_ID )
{
    $args = array( 
                    'ID'           => $post_ID, 
                    'post_title'   => 'My default title ...', 
                    'post_excerpt' => 'My default caption ...', 
                    'post_content' => 'My default description ...', 
            );

    wp_update_post( $args );

}
add_action( 'add_attachment', 'wpse_121709_upload_defaults' );

It should give you this result when you upload your file in the media uploader: