Add Open Graph to Meta Tags

functions.php

<?php 

/****************************************************************************************************************
 * ATTENTION! Don't copy the above line if you're going to use this in your functions.php - just the code below *
****************************************************************************************************************/

function fb_opengraph() {
    global $post;
 
    if(is_single()) { // article or post - not front page or archive
        if(has_post_thumbnail($post->ID)) {
            $img_src = wp_get_attachment_image_src(get_post_thumbnail_id( $post->ID ), 'medium');
            // if the post/page has a post thumbnail: use this
        } else {
            $img_src = get_stylesheet_directory_uri() . '/<path-to-default-image>/<default image>.jpg';
            /* else use the default image 
               edit with your data for the defaut image 
               the directory must be inside the theme directory */
        }
        if($excerpt = $post->post_excerpt) {
            $excerpt = strip_tags($post->post_excerpt);
            $excerpt = str_replace("", "'", $excerpt);
            // excerpt for the article - if any
        } else {
            $excerpt = get_bloginfo('description');
            // else use the blog description
        }
        ?>
 
    <meta property="og:title" content="<?php echo the_title(); ?>"/>
    <meta property="og:description" content="<?php echo $excerpt; ?>"/>
    <meta property="og:type" content="article"/>
    <meta property="og:url" content="<?php echo the_permalink(); ?>"/>
    <meta property="og:site_name" content="<?php echo get_bloginfo(); ?>"/>
    <meta property="og:image" content="<?php echo $img_src; ?>"/>
 
<?php
    } else {
        return;
    }
}
add_action('wp_head', 'fb_opengraph', 5);

/****************************************************************************************************************
 * ATTENTION! Don't copy the below line if you're going to use this in your functions.php - just the code above *
 ****************************************************************************************************************/
 
?>