Magento: how do I access custom variables in PHP?

I am aware of 'Custom Variables' and how they can be used with {{ }} brackets in email templates as well as in static blocks.

However, I want to use them in template code i.e. view.phtml.

I want to be able to access 'variable plain value' to retrieve a conversion value, i.e. a number/string as number for a given 'variable code'.