$re = '/(?:data-href=")(.*?)(?:">)/m';
$str = 'data-href="www.buxmob.net/index.php?id=577">
data-href="www.webopedia.com/TERM/K/keyword.html">
data-href="moz.com/beginners-guide-to-seo/keyword-research">';
preg_match_all($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