Inconsistent "UND" value in node fields

Question

I'm manually printing my node fields on its template (node--TYPE.tpl.php). Something like:

<div class="row">
    <div class="press-year col-md-12">
        <h2><?php print $year; ?></h2>
    </div>  
</div>

And my hook_preprocess_node() looks something like:

function MY_MODULE_preprocess_node(&$vars) {
    switch ($vars['type']) {
        case "my_type":
           if (isset($vars["field_year"]["und"][0])) {
              $vars["year"] = $vars["field_year"]["und"][0]["value"];
          }
        break;
    }
}

The output is fine to all fields; however, when I view the node as administrator, no output is printed. I listed all the variables from the hook to see what was happening with the following code.

function MY_MODULE_preprocess_node(&$vars) {
    var_dump($vars);
    ....
}

I'm getting all fields without the "UND" value, $vars["field_year"][0]["value"] instead of $vars["field_year"]["und"][0]["value"].

Do you have any clue why this happens?

Answer 1

I was having the same problem with D7. The solution for me was to use field_get_items(...) for reading the node data.

$year_items = field_get_items('node', $variables['node'], 'field_year');
$year = $year_items[0]['value'] + 1;

I found the post on Rendering Drupal 7 fields (the right way) very helpful. It does seem strange that we shouldn't use the $variables provided to the preprocessor and template to read and modify the template variables. I must be missing something.