Array error - can't reproduce documentation (theming views)

Hi,

Simply put, I can't print out the fields of a view, nor can I reproduce the variables a described in the docs of view 2.

Overriding a view (cf. theming) requires one to know the variables. The docs claim one does using

<?php
  dsm(array_keys($fields));
?>

That does not print anything in my view, and yes the dev is installed, nothing is cached. I get the error:

warning: array_keys() [function.array-keys]: The first argument should be an array in /xxx/local sites/website/sites/all/themes/zen/templates/views-view--Nodes--page-3.tpl.php on line 2

However, due to this post, I found out that another command does print the variables, namely:

<?php
  $test_var = 'at least print out this string!';
  dpm(get_defined_vars());
?>

This is not what the doc states. Quite as one would expect, one can not use the following to print the actual values:
print $fields['title']->content;

Does someone know what is going on here?