The best option, like shown in the example above, is to use two regular expressions. One to match the anchor tags and the other its attributes. The regular expression below does a standard match on a URL with an href attribute.
/<a.*href=((\"(.+)\".*>)|((\S+)((\s.*>)|>)))(.+)<\/a>/sU
But, if you want more attributes such as rel matched, I suggest you go for something like the function I've posted below. I use this to extract information about HTML forms and it seems to work OK on all but the most shoddy HTML code. To get all anchors on a page, use the following:
$anchors = get_html_tags($htmlCode, 'a');
// loop through and find anchors with rel="nofollow" attribute
foreach($anchors as $anchor) {
// link text, note: this may contain HTML
$text = $anchor['text'];
// look for rel in attributes array
if (array_key_exists('rel', $anchor['attirbutes']) &&
$anchor['attributes']['rel'] == 'nofollow') {
/* do stuff here */
}
}
The code for the get_html_tags() function is posted below:
/**
* Matches HTML tags in a string and their attributes.
*
* Returns array in the format:
* Array ([0] => Array ([text] => "text in between tags"
* [attributes] => Array ([attribute1] => [value],
* [attribute2] => [value])));
* @param $text string The string to find tags in.
* @param $tagname string The tag name of he tag to match e.g: form
* @param $clostag boolean Does the tag have corresponding close tags. i.e: </$tagname>
* @param $close_optional If a closetag may be missing, it is closed implicitly when another tag of the same name is found.
* include the name of an additional tags that closes the tag implicitly, here.
* @return array An indexed array, one element for each tag.
*
* @author Adam Delves <codedv @ sccode . com >
*/
function get_html_tags($text, $tagname, $closetag=true, $close_optional=false)
{
/* escape PCRE characters in tag name */
$tagname = preg_quote($tagname);
$ret = array();
/* regular expression to match mattributes in a tag name */
$attrib_match = "/((?i)[a-z]+) (\s*=\s* ( ((?U)(\"(.*)\")) |(\S+) ) |\s+) /sXi";
if ($closetag) {
if ($close_optional !== false) {
$close_optional = preg_quote($close_optional);
$regex = "/<$tagname(.*)>(.*)(<\/$tagname>|(?=<$tagname>)|(?=<\/$close_optional>))/Uis";
} else {
$regex = "/<$tagname(.*)>(.*)<\/$tagname>/Uis";
}
} else {
$regex = "/<$tagname((.+))\/?>/Uis";
}
// regex now matches the tag appropriatly
preg_match_all($regex, $text, $tags, PREG_SET_ORDER);
$tag_count = count($tags);
for($t = 0; $t < $tag_count; $t++) {
$tag = array();
/* get attributes */
preg_match_all($attrib_match, $tags[$t][1], $attributes, PREG_SET_ORDER);
$attribs = array();
$attrib_count = count($attributes);
for($a = 0; $a < $attrib_count; $a++) {
$name = strtolower(trim($attributes[$a][1]));
if (isset($attributes[$a][4])) { // name value pair found
$value = trim(isset($attributes[$a][7])?$attributes[$a][7]:$attributes[$a][6]);
} else {
$value = $name;
}
$attribs[$name] = $value;
}
$tag['attributes'] = $attribs;
if ($closetag) {
$tag['text'] = $tags[$t][2];
}
$ret[] = $tag;
}
return $ret;
}