gistfile1.txt

//Add Open Graph Meta Info from the actual article data, or customize as necessary
	function insert_fb_in_head() {
	    global $post;
	    if ( !is_singular()) //if it is not a post or a page
	        return;
	        //You'll need to find you Facebook profile Id and add it as the admin
	        echo '<meta property="fb:admins" content="XXXXXXXXX-fb-admin-id"/>';
	        echo '<meta property="og:title" content="' . get_the_title() . '"/>';
	        echo '<meta property="og:type" content="article"/>';
	        echo '<meta property="og:url" content="' . get_permalink() . '"/>';
	        // Customize the below with the name of your site
	        echo '<meta property="og:site_name" content="Your Site NAME Goes HERE"/>';
	        if(!has_post_thumbnail( $post->ID )) { //the post does not have featured image, use a default image
	        //Create a default image on your server or an image in your media library, and insert it's URL here
	        $default_image="http://example.com/image.jpg"; 
	        echo '<meta property="og:image" content="' . $default_image . '"/>';
	    }
	    else{
	        $thumbnail_src = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), 'medium' );
	        echo '<meta property="og:image" content="' . esc_attr( $thumbnail_src[0] ) . '"/>';
	    }
	    echo "
	";
	}
	add_action( 'wp_head', 'insert_fb_in_head', 5 );