Redirect Attachment Pages to Their Parent Post

<?php
if ( ! function_exists( 'scseed_redirect_attachment_pages' ) ) {
    function scseed_redirect_attachment_pages() {
        if ( ! is_attachment() ) {
            return;
        }
        global $post;
        if ( $post && $post->post_parent ) {
            $parent_url = get_permalink( $post->post_parent );
            if ( $parent_url ) {
                wp_redirect( esc_url( $parent_url ), 301 );
                exit;
            }
        }
        // No parent — redirect to the homepage.
        wp_redirect( esc_url( home_url( '/' ) ), 301 );
        exit;
    }
    add_action( 'template_redirect', 'scseed_redirect_attachment_pages' );
}