Not only is 0.00 a valid amount, but if you're just trying to verify a credit card is legitimate you are required by Visa and Mastercard to use that amount. A few years ago they stopped allowing pre-auths of any real value to be done for this reason. I think there are fines for merchants who fail to do so.
Having said that, if you're going to take the "charge $.01 and then void the transaction" route, the following code should work:
$transaction_id = $authorization->getTransactionID();
$void = new AuthnetAIM($apilogin, $apitranskey, true);
$void->setTransactionType("VOID");
$void->setParameter('x_trans_id', $transaction_id);
$void->process();