$re = '/(?<=xmlUrl=")[^"]*/i';
$str = '<outline type="rss" text="Tech Viral" title="Tech Viral" xmlUrl="http://feeds.feedburner.com/TechViral" htmlUrl="https://techviral.net"/>
<outline type="rss" text="The Verge" title="The Verge" xmlUrl="http://www.theverge.com/rss/full.xml" htmlUrl="https://www.theverge.com/"/>
<outline type="rss" text="Joystiq" title="Joystiq" xmlUrl="http://www.joystiq.com/rss.xml" htmlUrl="https://www.engadget.com/rss.xml"/>
<outline type="rss" text="BGR" title="BGR" xmlUrl="http://www.boygeniusreport.com/feed/" htmlUrl="http://bgr.com"/>';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php