API - PHP Variables

You need to specify the variable OUTSIDE the quotes

$armory = new BattlenetArmory($test,'Azjol-Nerub');

Or, if you have mod_string_replace enabled, you can do

$armory = new BattlenetArmory("$test",'Azjol-Nerub'); 

This will replace the $test inside the double quotes with the value of $test. This is unnecessary, because it will add useless processing requirements to your page, but it is useful if you want to create a string out of many variables. e.g.

$name="John Doe";
$age=35;
$country="USA";

$message="$name, age $age, lives in $country"; //Gives John Doe, age 35, lives in USA

Just to clear up the understanding here, dots are for concatenating strings. Like + in JS and & in VB.

$name = 'John';
echo 'hello there ' . $name . ', how are you?';

Weirdly in PHP you can put variables inside strings that are enclosed by double quotes and they will be replaced by values - so this will work (with a very slight performance drop).

$name = 'John';
echo "hello there $name, how are you?";

The thing was never going to work, PHP loads up all code between those tags at the start, parses them and then begins to do its job. It has no meaning after that.

So the answer to your question is as someone else said above - just thought I'd explain:

$test='EU'; 
$armory = new BattlenetArmory($test, 'Azjol-Nerub'); //ex. ('US', 'Exodar')