class The_Class {

    private $_products = 3;

    public function __construct() {
        $this->_products = 'foo';
    }
}

$instance_of_class = new The_Class();
$reflClass = new ReflectionClass($instance_of_class);
$member = $reflClass->getProperty('_products');
$member->setAccessible(true);
var_dump($member->getValue($instance_of_class)); // string(3) "foo"