The Nutz

I modified a little bit your code because some posts from my webpage are created automatically and contain just photos. So i need the og:image meta tag to find these images and add them automatically.

I will share this code for those who need this function.

// Image
        if (function_exists('has_post_thumbnail') && has_post_thumbnail()) {
            $thumbnail_info = wp_get_attachment_image_src( get_post_thumbnail_id($post->ID), 'thumbnail' );
            $metadata_arr[] = '<meta property="og:image" content="' . $thumbnail_info[0] . '" />';
            //$metadata_arr[] = '<meta property="og:image:secure_url" content="' . str_replace('http:', 'https:', $thumbnail_info[0]) . '" />';
            $metadata_arr[] = '<meta property="og:image:width" content="' . $thumbnail_info[1] . '" />';
            $metadata_arr[] = '<meta property="og:image:height" content="' . $thumbnail_info[2] . '" />';
        }
			else {
				global $post, $posts;
				$first_img = '';
				ob_start();
				ob_end_clean();
				$output = preg_match_all('/<img.+src=[\'"]([^\'"]+)[\'"].*>/i', $post->post_content, $matches);
				$first_img = $matches [1] [0];

					if(empty($first_img)){
					$metadata_arr[] = '<meta property="og:image" content="' . trim($options["default_image_url"]) . '" />';
					}else {
					$metadata_arr[] = '<meta property="og:image" content="' . $first_img . '" />';
						}
			}
		if ( is_attachment() && wp_attachment_is_image($post->ID) ) { // is attachment page and contains an image
            $attachment_image_info = wp_get_attachment_image_src( get_post_thumbnail_id($post->ID), 'large' );
            $metadata_arr[] = '<meta property="og:image" content="' . $attachment_image_info[0] . '" />';
            //$metadata_arr[] = '<meta property="og:image:secure_url" content="' . str_replace('http:', 'https:', $attachment_image_info[0]) . '" />';
            $metadata_arr[] = '<meta property="og:image:width" content="' . $attachment_image_info[1] . '" />';
            $metadata_arr[] = '<meta property="og:image:height" content="' . $attachment_image_info[2] . '" />';
        }