zend session namespace not working

Question

I am unable to access zend session in included file via layout.

what i have done so far -

//bootstrap      
public function _initSession()
    {
      Zend_Session::start();
      $test = new Zend_Session_Namespace('test');

    }

//controller
public function init(){
        $test = new Zend_Session_Namespace('test');
        $test->abc = 'defghi';
}

//layout include file
 <?php include_once(  APPLICATION_PATH . '/data/ga_test.php');?>

//ga_test.php

$test = new Zend_Session_Namespace('test');
echo 'this is ' . $test->abc;

I am not able to access the variable in ga_test file. I am getting an empty variable. But if I include ga_test end of each view file then it works. Obviously I don't want to go to every view file and include ga_test.php. Can I do this via layout.

I am sure, I am doing something wrong here. Any help would be really appreciated.

Thanks