If you would like to make a "one off" charge against a subscribed customer's credit card, you may use the charge method:

$user->charge(100);

The charge method accepts the amount you would like to charge in the lowest denominator of the currency. So, for example, the example above will charge 100 cents, or $1.00, against the user's credit card.

The charge method accepts an array as its second argument, allowing you to pass any options you wish to the underlying Stripe charge creation:

$user->charge(100, [
    'source' => $token,
    'receipt_email' => $user->email,
]);

The charge method will return false if the charge fails. This typically indicates the charge was denied:

if ( ! $user->charge(100))
{
    // The charge was denied...
}

If the charge is successful, the full Stripe response will be returned from the method.