Adding open graph tags to node page

<?php
   
//custom.module: function custom_preprocess_node(&$vars) {
   
drupal_add_html_head(array(
     
'#tag' => 'meta',
     
'#attributes' => array(
       
'property' => 'og:description',
       
'content' => trim(strip_tags($vars['node']->body['und'][0]['safe_value'])),
      ),
    ),
'og_description');
?>
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