Unable to transfer php logic from node--post-esl-material.tpl.php to template.php

Question

If I use the following code in template.php and print $link in node--post-esl-material.tpl.php, everything works fine; I get "hey baby."

function eslmooc_preprocess_node(&$vars, $hook) {
   if ($vars['type'] == 'post_esl_material'){
      $vars['link'] ='hey baby';
   }
}

However, if I use the following code and print $link in node--post-esl-material.tpl.php, it doesn't print anything.

function eslmooc_preprocess_node(&$vars, $hook) {
   if ($vars['type'] == 'post_esl_material'){
      $xyz = '';
      if (empty($content['field_link']))
         $xyz .= '';    
      else {
         $xyz .= '<div class="link">';
          $xyz .= '<h4>LINK</h4>';
           $xyz .= '<div class="field_link">';
            $xyz .= $content['field_link']; 
           $xyz .= '</div>';
         $xyz .= '</div>';
      }
      $vars['link'] = $xyz;
   }
}

I cannot get the PHP logic to work. Can anyone see a mistake within the code?

Answer 1

I think that the problem is that $content is not defined there. You have it only inside the template file but not in the preprocess hook.

Answer 2

The following code works:

function eslmooc_preprocess_node(&$vars, $hook) {
   if ($vars['type'] == 'post_esl_material'){
      $xyz = '';
      $node = $vars['node'];
      $field_link = field_view_field('node', $node, 'field_link');

      if (empty($field_link))
         $xyz .= '';    
      else {
     $xyz .= '<div class="link">';
       $xyz .= '<h4>LINK</h4>';
         $xyz .= '<div class="field_link">';
           $xyz .= drupal_render($field_link);
         $xyz .= '</div>';
     $xyz .= '</div>';
      }

      $vars['link'] = $xyz;
   }
}