Redirect Missing Pages to the Nearest Parent Page

// Status code: 301 (permanent) or 302 (temporary).
$wpide_parent_redirect_status = 301;

add_action( 'template_redirect', function () use ( $wpide_parent_redirect_status ) {
    if ( ! is_404() || ! get_option( 'permalink_structure' ) ) {
        return;
    }

    $path = isset( $_SERVER['REQUEST_URI'] ) ? (string) wp_parse_url( wp_unslash( $_SERVER['REQUEST_URI'] ), PHP_URL_PATH ) : '';
    $base = untrailingslashit( (string) wp_parse_url( home_url(), PHP_URL_PATH ) );
    $path = trim( substr( $path, strlen( $base ) ), '/' );

    // Skip missing files such as images and scripts, and very deep or empty paths.
    if ( '' === $path || preg_match( '/\.[a-z0-9]{2,5}$/i', $path ) || substr_count( $path, '/' ) > 6 ) {
        return;
    }

    $parts = explode( '/', $path );

    while ( count( $parts ) > 1 ) {
        array_pop( $parts );

        $url = home_url( user_trailingslashit( implode( '/', $parts ) ) );

        if ( url_to_postid( $url ) || get_page_by_path( implode( '/', $parts ) ) ) {
            wp_safe_redirect( $url, (int) $wpide_parent_redirect_status );
            exit;
        }

        $term = get_term_by( 'slug', end( $parts ), 'category' );

        if ( $term && untrailingslashit( get_term_link( $term ) ) === untrailingslashit( $url ) ) {
            wp_safe_redirect( $url, (int) $wpide_parent_redirect_status );
            exit;
        }
    }
} );