my session are not active when changing page code example

Example: php start a session

session_start();
if(!isset($_SESSION["started"]){ //Check if the session already exist
    //If it does not exist we append attributes we need in
	$_SESSION["started"] = true;
  	$_SESSION["attribute_1"] = $value_1;  
  	...
    $_SESSION["attribute_n"] = $value_n;      
}