why php session variable is empty in safari browser by Deepa

Depending on my session variable i want to show my form .IT Works fine with Chrome and IE but session value of $_SESSION['shop'] is getting empty in safari and couldn't work .

I used following code. Please help me out to know why it is not working on safari.

 header('P3P:CP="IDC DSP COR ADM DEVi TAIi PSA PSD IVAi IVDi CONi HIS OUR IND CNT"');
 session_start();

//checking whether it is in session or not.

if(isset($_SESSION['shop']) && !empty($_SESSION['shop']))

{ 

}