Add an attachment to the Order Approved Notification email

Hello,

Thank you for the useful plugin.

I would like to add an attachment to the Order approved notification email that is sent to the client.

One way I could do it is to add a code snippet to the functions.php file of the parent’s theme that would target this particular email.

The code snippet I use is the following one:

add_filter( 'woocommerce_email_attachments', 'attach_file_to_emails', 10, 4 );
 
function attach_file_to_emails( $attachments, $email_id, $order, $email ) {
    $email_ids = array( 'WC_Customer_Order_Approved' );
    if ( in_array ( $email_id, $email_ids ) ) {
        $upload_dir = wp_upload_dir(); 
        $attachments[] = $upload_dir['basedir'] . "/2021/03/ticket.pdf"; 
    }
    return $attachments;
}

This way, the file ticket.pdf would be automatically included as the email attachment.

However, this doesn’t work.

I wonder if the approach is good and what is missing in the code?

Thanks.