Using session_start() in order to pass varriables to external application

I am using a blank application and all i want is to pass the $_SESSION[‘variable1’] = “Testing”; to an external php file to the same domain that is my scriptcase project…

On top of my script i have placed the session_start() and then did
$_SESSION['variable1'] = "Testing";

Then i have a <a href="www.test.com.gr" target="_blank">My_link</a>
I click the link, a new page appears but when i echo the session variable, it’s not beeing displayed…

Any ideas ?