DOMDocument PHP Memory Leak

Running PHP 5.3.6 under MAMP on MAC, the memory usage increases every x calls (between 3 and 8) until the script dies from memory exhaustion. How do I fix this?

libxml_use_internal_errors(true);
while(true){
 $dom = new DOMDocument();
 $dom->loadHTML(file_get_contents('http://www.ebay.com/'));
 unset($dom);
 echo memory_get_peak_usage(true) . '<br>'; flush();
}