Adding Open Graph to Wordpress

/* Open graph
https://www.elegantthemes.com/blog/tips-tricks/how-to-add-open-graph-tags-to-wordpress
http://stackoverflow.com/a/14359678
http://wordpress.stackexchange.com/a/141136
http://telegram.me/webpagebot
*/

function t_opengraph() {
    global $post;
    $post_thumbnail_id = get_post_thumbnail_id($post->ID);
    $post_thumbnail_url = wp_get_attachment_url( $post_thumbnail_id );
     if(is_single()) {
        if($excerpt = $post->post_excerpt) {
            $excerpt = strip_tags($post->post_excerpt);
            $excerpt = str_replace("", "'", $excerpt);
        } else {
            $excerpt = get_bloginfo('description');
        }
        ?>

    <meta property="og:title" content="<?php echo the_title(); ?>"/>
    <meta property="og:description" content="<?php echo $excerpt; ?>"/>
    <meta property="og:image" content="<?php echo $post_thumbnail_url; ?>"/>

<?php
    } else {
        return;
    }
}
add_action('wp_head', 't_opengraph', 5);