WordPress is Not Setting PHP $_POST on Custom Ajax

I’m having some doubts about your code. IF your using WordPress you should use https://codex.wordpress.org/Plugin_API/Action_Reference/wp_ajax_(action)

So you no session.php, but a function:

add_action( 'wp_ajax_foobar', 'my_ajax_foobar_handler' );

function my_ajax_foobar_handler() {
    $u = $_POST["url"];
    $p = $_POST["product"];
    echo $u . "  " .$p ;
    wp_die();
}

and simplify yours JS

jQuery.post(
    my_foobar_client.ajaxurl, 
    {
        'action': 'foobar',
        'url' : 'www.google.com', 
        'product' : 'Map' 
    }, 
    function(response) {
        console.log(response);
    }
);