A user can have several types of subscriptions: channel subscription, tag subscription, or favorites subscription. A Zend_Gdata_YouTube_SubscriptionEntry is used to represent individual subscriptions.
To retrieve all subscriptions for the user 'liz':
Example 453. Retrieving all subscriptions for a user
<?php
$yt = new Zend_Gdata_YouTube();
$subscriptionFeed = $yt->getSubscriptionFeed('liz');
foreach ($subscriptionFeed as $subscriptionEntry) {
echo $subscriptionEntry->title->text . "\n";
}