Variable name as a string in Javascript

Is there a way to get a variable name as a string in Javascript? (like NSStringFromSelector in Cocoa)

I would like to do like this:

var myFirstName="John";
alert(variablesName(myFirstName) + ":" + myFirstName);

--> myFirstName:John

UPDATE

I’m trying to connect a browser and another program using JavaScript. I would like to send instance names from a browser to another program for callback method:

FooClass = function(){};
FooClass.someMethod = function(json) {
  // Do something
}

instanceA = new FooClass();
instanceB = new FooClass();
doSomethingInAnotherProcess(instanceB); // result will be substituted by using instanceB.someMethod();

...

From another program:

evaluateJavascriptInBrowser("(instanceName).someMethod("resultA");");

In PHP:
How to get a variable name as a string in PHP?