Código PHP:
<?php
$patron = "/<a href=\"()\"/";
$string = '<div class="thumb"><a href="/fire_beach_widescreen-wallpapers.html"><em>1178 downloads</em><img src="/thumbs/fire_beach_widescreen-t1.jpg" alt="Fire Beach Widescreen Wallpaper" class="thumb_img"><span class="mini-tags"><span class="tag-wide tips" title="Fire Beach Widescreen :: Wide Wallpaper"></span></span></a><br><a href="/fire_beach_widescreen-wallpapers.html" title="Fire Beach Widescreen Wallpaper" class="thumblink">Fire Beach Widescreen</a></div>';
preg_match( $patron, $string, $matches );
?>