$re = '/(?=.*displayname)(?=.*templateid).*/';
$str = '<where>
<equals xmlns="http://xml.newview.com/sn/General/Expression">
<attribute displayname="document_status" templateid="556">NA_LOC_Location.system.document_status</attribute>
<value>\'Active\'</value>
</equals>
</where>
<where>
<equals xmlns="http://xml.newview.com/sn/General/Expression">
<attribute templateid="556" displayname="document_status">NA_LOC_Location.system.document_status</attribute>
<value>\'Active\'</value>
</equals>
</where>';
preg_match_all($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