preprocessor example

node--blog.tpl.php

<div>
  <?php print $name_of_var; ?>
</div>

theme-template.php

<?php

/**
 * Implements template_preprocess_node().
 */

function mytheme_preprocess_node(&$variables) {
  if ('blog' == $variables['type']) {
    mytheme_preprocess_node_blog($variables);
  }
}

function mytheme_preprocess_node_blog($variables) {
  $variables['name_of_var'] = filter_xss($block_var);
}
}