bbp_update_reply_id( int $post_id,  $reply_id )

function bbp_update_reply_id( $post_id, $reply_id ) {

	// Allow the reply ID to be updated 'just in time' before save
	$reply_id = apply_filters( 'bbp_update_reply_id', $reply_id, $post_id );

	// Update the post meta reply ID
	update_post_meta( $post_id, '_bbp_reply_id',(int) $reply_id );
}