To get access to a variable inside the template you need to set it first.
You can set template variables with the function setVariable(). A dirty example:
$tpl->setVariable( 'globals', $GLOBALS );
This will set the template variable globals, {$globals}, to the value of all global PHP variables.
However I would not recommend using the GLOBALS direcly, you should use the functions in eZHTTPTool to fetch variables. E.g. postVariable() should be used to fetch HTTP post variables.
