function my_get_tags_sitemap(){
if ( !function_exists('wp_tag_cloud') || get_option('cb2_noposttags')) return;
$unlinkTags = get_option('cb2_unlinkTags');
echo '<div class="tags"><h2>Tags</h2>';
$ret = []; // here you need to add array which you call inside implode function
if($unlinkTags)
{
$tags = get_tags();
foreach ($tags as $tag){
$ret[]= $tag->name;
}
//ERROR OCCURS HERE
echo implode(', ', $ret);
}
else
{
wp_tag_cloud('separator=, &smallest=11&largest=11');
}
echo '</div>';
}