Google Groups Provisioning API with PHP (Zend). Memory usage improvements.

retrieveAllRecipients.php

/**
 * Retrieve all recipients for a given email list using as little memory as 
 * possible (or at least less than the default Zend one which is known to hog a bit)
 * 
 * !!! DO NOT USE Zend_Gdata_Gapps::retrieveAllRecipients !!!
 * 
 * @param Zend_Gdata_Gapps $gapps Reference to Zend_Gdata_Gapps object
 * @param array $members Reference to array of member email addresses
 * @param string $emaiList The email list from which members should be retrieved
 * @param string $startRecipient Get next page of recipients starting from this email
 */
function retrieveAllRecipients(&$gapps, &$members, $emailList, $startRecipient = null) {
    // For memory comparison purposes
    // echo '<br/>MEMORY: '.memory_get_usage();
    // echo '<br/>MEMORY REAL: '.memory_get_usage(true);
    // echo "<br/>$emailList + $startRecipient";
        
    $feed = $gapps->retrievePageOfRecipients($emailList, $startRecipient);
    foreach ($feed as $entry) {
        // This is where our main memory improvement is compared to 
        // Zend_Gdata_Gapps::retrieveAllRecipients. We know we only need
        // email address. No need to store the entire $entry object
        $members[] = $entry->who->email;
    }

    $next = $feed->getLink('next');
    
    // This is the other main memory improvement. Each feed object takes ~1MB
    // of memory. Our listserv with 4500+ members would require 45 page calls
    // and thus 45MB of memory using the Zend retrieveAllRecipients method.
    // Unsetting our feed object before recursively calling our retrieveAllRecipients
    // keeps memory usage relatively flat.
    unset($feed);
    
    if ($next !== null) {
        // href will look like: https://apps-apis.google.com/a/feeds/ctsacentral.org/emailList/2.0/apisynctest/recipient/?startRecipient=test190%40example.com
        if(strpos($next->href, 'startRecipient=')) {
            
            $hrefParts = explode('startRecipient=', $next->href);
            // Retrive all recipients starting with the email address test190%40example.com
            retrieveAllRecipients(&$gapps, &$members, $emailList, $hrefParts[1]);
            
        } else {
            trigger_error('startRecipient not found. Could not get next page of recipients. There is a possiblity that the retrieveAllRecipients function did not return all recipients/members. You should investigate.', E_USER_ERROR);
        }
    }

}

I needed to retrieve all email addresses belonging to a Google Group using the Provisioning API. My group had ~5000 members memory usage became an issue. This function is meant to be called instead of Zend_Gdata_Gapps::retrieveAllRecipients