You have a BRAND NEW CAR
<?php

session_start();

if (isset($_SESSION['car']))
{
    echo "Mileage: " . $_SESSION['car']->mileage . "\n";
    $_SESSION['car']->drive();
}else
{
    $_SESSION['car'] = new car();
    echo "You have a BRAND NEW CAR\n";
}


class car
{
    public $mileage;
    public function __construct()
    {
        $this->mileage = 0;
    }

    public function drive()
    {
        $this->mileage++;
    }

}

highlight_file(__FILE__);