Tipycal scenario. Imagine you need to know which variables yo need in a concret place of your site, say /blog, a node or a view. Very easy, simple add a block, for example at your foot if available in your theme, with php input availabe, and this code:
<?php print '<pre>'; var_dump(get_defined_vars()); print '</pre>';?>
Now, make it only available for your role, for example, and place it where you prefer (foot for example).