The first step is to add a function that lets social media platforms know you are using the Open Graph protocol. It alerts these platforms to the presence of our Open Graph functions and it helps them be able to read the meta we will add in a second. There is no need to change any of the code. It can be pasted into your functions.php file. The path to the functions.php file is root -> wp-content -> themes -> “active theme name” -> functions.php.

function doctype_opengraph($output) {
    return $output . '
    xmlns:og="http://opengraphprotocol.org/schema/"
    xmlns:fb="http://www.facebook.com/2008/fbml"';
}
add_filter('language_attributes', 'doctype_opengraph');

The next step is to dynamically add Open Graph information to each post and page on your site. That is done by pasting the following code into your functions.php file below the code you just added. The only thing that needs to be changed is the default Open Graph Image. This image will show if there is no featured image on the page or post. Just paste the url of the image you want where I have written URL-OF-DEFAULT-IMAGE-GOES-HERE.

function opengraph_function() {
    global $post;

    if(is_single()) {
        if(has_post_thumbnail($post->ID)) {
            $img_src = wp_get_attachment_image_src(get_post_thumbnail_id( $post->ID ), 'medium'); // Get page or post featured image
        } else {
            $img_src = 'URL-OF-DEFAULT-IMAGE-GOES-HERE'; // Set Default image if featured image doesn't exist.
        }
        if($excerpt = $post->post_excerpt) {
            $excerpt = strip_tags($post->post_excerpt); // Get excerpt
            $excerpt = str_replace("", "'", $excerpt); // Format excerpt
        } else {
            $excerpt = get_bloginfo('description'); // Get site description if no excerpt exists
        }
        ?>   
        <meta property="og:title" content="<?php echo the_title(); ?>"/> // The title that will show up in social media
        <meta property="og:description" content="<?php echo $excerpt; ?>"/> // The excerpt that will show up in social media
        <meta property="og:type" content="article"/> // The content that will show up in social media
        <meta property="og:url" content="<?php echo the_permalink(); ?>"/> // The link that will show up in social media
        <meta property="og:site_name" content="<?php echo get_bloginfo(); ?>"/> // The website title that will show up in social media
        <meta property="og:image" content="<?php echo $img_src; ?>"/> // The image that will show up in social media

      <?php
          } else {  
              return;       //if it is not a page or a post don't print any data
            }  
      }  
      add_action('wp_head', 'opengraph_function', 5); // adds code to the head of every page and post