Php 从Facebook rss源提取外部图像url

我有一个Facebook页面提要，看起来像这样

http://external.ak.fbcdn.net/safe_image.php?d=AQA-U_vFlmf0YW5c&w=130&h=130&url=http%3A%2F%2Fi1.ytimg.com%2Fvi%2FX9Hx6nUTSwE%2Fmaxresdefault.jpg%3Ffeature%3Dog

如何提取&url………featuredog（仅提取图像url）之间的内容？

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欣赏任何代码示例。

我的正则表达式很难看，但却能做到：

<?php
$str = 'http://external.ak.fbcdn.net/safe_image.php?d=AQA-U_vFlmf0YW5c&w=130&h=130&url=http%3A%2F%2Fi1.ytimg.com%2Fvi%2FX9Hx6nUTSwE%2Fmaxresdefault.jpg%3Ffeature%3Dog';

$str = urldecode($str);
preg_match_all('~&url=(.*?)[\?\!]?feature~i', $str, $matches, PREG_PATTERN_ORDER);

echo $matches[1][0];
?>

$parts = parse_url('http://external.ak.fbcdn.net/safe_image.php?d=AQA-U_vFlmf0YW5c&w=130&h=130&url=http%3A%2F%2Fi1.ytimg.com%2Fvi%2FX9Hx6nUTSwE%2Fmaxresdefault.jpg%3Ffeature%3Dog');
parse_str($parts['query'], $params);
var_dump($params['url']);