Handling unparsed placeholders

Hey!

One thing I missed in your draft is the handling of placeholders, which
aren't assigned a value to. The PHPLib Template class allows you to specify
a $unknowns variable in the class' constructor, which defines how to handle
placeholders which aren't used in your script. This is a nice feature for
debugging and error handling.

Also, I don't understand the configuration variables part of your draft. Are
these configuration directive specific to the template module, or do you
mean PHP configuration?

And a tpl_print() would be a nice shorthand.

-Tobias