Wordpress open graph image tag

<?php if (is_single()&& has_post_thumbnail()) { ?>

  <meta property="og:image" content="<?php $src = wp_get_attachment_image_src( get_post_thumbnail_id($post->ID), array( 300, 300 ), false, '' ); echo $src[0]; ?>" />
  <meta property="og:image:width" content="200" />
  <meta property="og:image:height" content="200" />

<?php }else{ ?>

  <meta property="og:image" content="<?php bloginfo('siteurl'); ?>/wp-content/themes/MyTheme/images/preview.jpg" />
  <meta property="og:image:width" content="200" />
  <meta property="og:image:height" content="200" />

<?php } ?>