With REQUEST_URI i get id node or alias path? I have a big doubt. In template.php I am using:

$_SERVER['REQUEST_URI']

what will the output like:  node/id-numberor /Alias_page ?
The right way to check on which page are you, is to use the current_path() function. Below is an example:

if (current_path() == 'your/system/path') {
  // Do whatever.
}


This is the best way because aliases can change, while system paths stay the same.

However, if you really need the aliased path, use the drupal_get_path_alias() function instead.