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<?php
  print print_r(array_keys($fields), 1);

  // Or if you have the developer module installed
  dsm(array_keys($fields));
?>

<?php if (isset($fields['field_employee_portrait']->content)): ?>
<div class="author-photo">
  <?php print $fields['field_employee_portrait']->content; ?>
</div>
<?php endif; ?>