Wordpress - adsense inside posts

Here is sample code for Wordpress widget. With this widget You can place random posts + Google adsense code inside single post.

Rule for showing this box is : If img = 600px , after H2 show box ; else do nothing

And code goes like this:

public function sadrzaj_dodaj_widget($content) {
        if(is_single()) {
            global $post;
            if(has_post_thumbnail($post->ID)) {
                $post_thumbnail_id = get_post_thumbnail_id( $post->ID );
                list($slika_sirina, $slika_visina, $slika_tip, $slika_attr) = getimagesize( get_attached_file( $post_thumbnail_id ) );
                if($slika_sirina == 600) {
                    //Filtriranje samo ako je post
                    $html .= preg_replace('/<\/h{1}2>/', '</h2>'.$this->html_widgeta(), $content, 1);
                    return $html;
                }
            }
        }
        return $content;
    }