How to get total Facebook shares and likes

Step 1: Create a facebook app

1. Go to Facebook Developers page and click Add a New App link.

2. After clicking that link a popup will appear. Input any App Name, your Contact Email and select Category.
3. Get App ID and App Secret on this page (also add your site's url):

4. The last step is to make your facebook application public.

So, that’s it, in all examples in this post our Access Token will look like this: Application ID|App Secret.

Step 2: Add the counter to the site

Use the following php function (inside your theme's functions.php):

/**
 * Display number of shares using WordPress HTTP API
 *
 * @param integer $post_id We want to get number of shares of the post with this ID
 */
function wp_get_shares( $post_id ) {
    $cache_key = 'misha_share' . $post_id;
    $access_token = 'APP_ID|APP_SECRET';
    $count = get_transient( $cache_key ); // try to get value from Wordpress cache

    // if no value in the cache
    if ( $count === false ) {
        $response = wp_remote_get('https://graph.facebook.com/v2.7/?id=' . urlencode( get_permalink( $post_id ) ) . '&access_token=' . $access_token );
        $body = json_decode( $response['body'] );
        //print_r($body);

        $count = intval( $body->share->share_count );
        set_transient( $cache_key, $count, 3600 ); // store value in cache for a 1 hour
    }
    return $count;
}

Call it using:

echo wp_get_shares(get_the_ID());

Source: https://rudrastyh.com/facebook/get-share-count-for-url.html#facebook_app
For other social media sources: https://gist.github.com/jonathanmoore/2640302