Contextual value when the filter is not available and PHP code I have block view that should be rendered in the node details page. i.e /node/*. The block should render latest 6 nodes published under the Category category_field that the node has its value.
However, the URL is rewritten and the category id tid is not available. The URL is looks like the following:
http://example.com/Category/world/the-node-title
So the contextual filter is not available in the URL. So, I created the following PHP code, shown in the screen shot, to get the category tid and return it:

In the node.tpl.php when I try to var_dump($node-&gt;field_category['und'][0]['tid']); it returns the number of tid of the current node. However, the above demonstrated code seems to be not work in the PHP filter code. When I try to return any available value for an category id such as 19 for example, it works.
In other words, how could I return the current node's category field id to the filter?
I found the cause of the problem from this resource and I have to define the $node variable by:

$node = node_load(arg(1));


Then I use the $node as shown in the question above.