[RegExp] extracting anchors

Hello, I want to extract the "name"-attribute of all anchors out of an HTML-source-code which don't have the "href"-attribute. I can use this code to get the "name"-attribute: preg_match_all('/<a([^>]*?)name=[ \'\"](.*?)[ \'\"](.*?)>/is',$src,$ar); The name-attributes are now in $ar[2]. How can I exclude all links which have the href-attribute? I didn't find an easy way how to say that a string must _not_ be part of a pattern match. I hope you can give me some advise. Jens