Customize robots.txt Output

<?php
if ( ! function_exists( 'scseed_custom_robots_txt' ) ) {
    function scseed_custom_robots_txt( $output, $public ) {
        if ( '0' === $public ) {
            // Site is set to discourage search engines — leave robots.txt as-is.
            return $output;
        }

        $sitemap_url = esc_url( home_url( '/wp-sitemap.xml' ) );

        $output  = "User-agent: *
";
        $output .= "Disallow: /wp-admin/
";
        $output .= "Disallow: /wp-login.php
";
        $output .= "Disallow: /xmlrpc.php
";
        $output .= "Disallow: /wp-includes/
";
        $output .= "Disallow: /search/
";
        $output .= "Disallow: /?s=
";
        $output .= "Allow: /wp-admin/admin-ajax.php
";
        $output .= "
";
        $output .= "Sitemap: {$sitemap_url}
";

        return $output;
    }
    add_filter( 'robots_txt', 'scseed_custom_robots_txt', 10, 2 );
}