how do you add more variables for head.tpl?

[cbarg2004]

If in storefront/view/default_html5/template/common/head.tpl I enter the line

print_r (get_defined_vars());

I get an array of all defined variables. Now, how can I add extra variables? Where (what file) those variables are defined and populated?
I know the query, I just don't know where to write it.

Thanks

[abantecart]

i am not clear what variables you look for? Some variable are specific to common, page or block controller

For head, see this controller:
https://github.com/abantecart/abantecart-src/blob/master/public_html/storefront/controller/common/head.php

[cbarg2004]

Basically I need to get the image of the product url within the head tags for Facebook metatags. I just did it opening a connection in the head.tpl but I don't quite like the idea :-/

[eCommerce Core]

If this data comes from facebook based on direct access to facebook URL, it needs to be in 'tpl' file

[cbarg2004]

No, the image URL corresponding to the article you are viewing is in resources, and the URL is in the database (resource_description.resource_path). I had to do a query, even though I didn't want to :-/ but it's working :-)