PHP Regular Expression Extracts the function of web page hyperlink url

function match_links($document) {
preg_match_all("'<\s*a\s.*?href\s*=\s*([\"\'])?(?(1)(.*?)\\1|([^\s\>]+))[^>]*>?(.*?)</a>'isx",$document,$links);
while(list($key,$val) = each($links[2])) {
if(!empty($val))
$match['link'][] = $val;
}
while(list($key,$val) = each($links[3])) {
if(!empty($val))
$match['link'][] = $val;
}
while(list($key,$val) = each($links[4])) {
if(!empty($val))
$match['content'][] = $val;
}
while(list($key,$val) = each($links[0])) {
if(!empty($val))
$match['all'][] = $val;
}
return $match;
}