$re = '/\<h1(.*(class="(?P<class>.+)"?).*|)\>(?P<text>[^\<]+)\<\/h1\>/';
$str = '<h1
class="sdkfjh">fhgkfg</h1>
<h1 class=\'sdkfjh\'>askjdhsdkj</h1>
<h1
style="gjh" class="sdkfjh">askjdhsdkj</h1>';
preg_match_all($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