Parsing HTML href-Attribute

Hey, I want to "parse" a href-attribute in a given String to check if there is a relative link and then adding an absolute path. Example: $string = '<a class="sample" [...additional attributes...] href="/foo/bar.php" >'; I tried using regular expressions but my knowledge of RegEx is very limited. Things to consider: - $string could be quite long but my concern are only those href attributes (so working with explode() would be not very handy) - Should also work if href= is not using quotes or using single quotes - link could already be an absolute path, so just searching for href= and then inserting absolute path could mess up the link Any ideas? Or can someone create a RegEx to use? Thanks