<?php
$hrefs = '<a href="sitename1">xyz …</a>
<a href="sitename2">xyz …</a>';
$r = '/(?<=href=").*?(?=">)/';
$sitename = 'sitename.html';
echo $result;
PD9waHAKCiRocmVmcyA9ICc8YSBocmVmPSJzaXRlbmFtZTEiPnh5eiDigKY8L2E+CjxhIGhyZWY9InNpdGVuYW1lMiI+eHl6IOKApjwvYT4nOwokciA9ICcvKD88PWhyZWY9IikuKj8oPz0iPikvJzsKJHNpdGVuYW1lID0gJ3NpdGVuYW1lLmh0bWwnOwokcmVzdWx0ID0gcHJlZ19yZXBsYWNlKCRyLCAkc2l0ZW5hbWUsICRocmVmcyk7CmVjaG8gJHJlc3VsdDs=