regular expression tog et values of html tag attributes

Question

<li class="zk_list_c2 f_l"><a title="abc" target="_blank" href="link">
                                        abc
                                    </a>&nbsp;</li>

how would i extract abc and link?

$pattern="/<li class=\"zk_list_c2 f_l\"><a title=\"(.*)\" target=\"_blank\" href=\"(.*)\">\s*(.*)\s*<\/a>&nbsp;<\/li>/m";
preg_match_all($pattern, $content, $matches);

the one i have right now doesnt seems to work

@Hao: Have you seen this similar question? http://stackoverflow.com/questions/1732348/regex-match-open-tags-except-xhtml-self-contained-tags/1732454 — jwismar, Mar 27 '10 at 16:37

Pascal MARTIN · Answer 1 · 2010-03-27T17:10:56.190

Considering your are trying to extract some data from an HTML string, regex are generally not the right/best tool for the job.

Instead, why no use a DOM parser, like the DOMDocument class, provided with PHP, and its DOMDocument::loadHTML method ?

Then, you could navigate through your HTML document using DOM methods -- which is much easier than using regex, especially considering than HTML is not quite regular.

Here, for example, you could use something like this :

$html = <<<HTML
<li class="zk_list_c2 f_l"><a title="abc" target="_blank" href="link">
        abc
    </a>&nbsp;</li>
HTML;

$dom = new DOMDocument();
$dom->loadHTML($html);
$as = $dom->getElementsByTagName('a');
foreach ($as as $a) {
    var_dump($a->getAttribute('href'));
    var_dump(trim($a->nodeValue));
}

And you would get the following output :

string(4) "link"
string(3) "abc"

The code is not quite hard, I'd say, but, in a few words, here what it's doing :

Load the HTML string : DOMDocument::loadHTML
Extract all <a> tags : DOMDocument::getElementsByTagName
Foreach tag found :
- get the href attribute : DOMElement::getAttribute
- and the value of the node : DOMNode::$nodeValue

Just a note : you might want to check if the href attribute exists, with DOMElement::hasAttribute, before trying to use its value...

EDIT after the comments : here's a quick example using DOMXpath to get to the links ; I supposed you want the link that's inside the <li> tag with class="zk_list_c2 f_l" :

$dom = new DOMDocument();
$dom->loadHTML($html);

$xpath = new DOMXPath($dom);
$as = $xpath->query('//li[@class="zk_list_c2 f_l"]/a');

foreach ($as as $a) {
    var_dump($a->getAttribute('href'));
    var_dump(trim($a->nodeValue));
}

And, again, you get :

string(4) "link"
string(3) "abc"

As you can see, the only thing that changes is the way you're using to get to the right <a> tag : instead of DOMDocument::getElementsByTagName, it's just a matter of :

instanciating The DOMXPath class
and calling DOMXPath::query with the right XPath query.

@hao : then, maybe an XPath query, instead of getElementsByTagName, could do the trick ? *(see http://www.php.net/manual/en/domxpath.query.php )* ;; anyway, I would really not use regex for this kind of data-extraction. — Pascal MARTIN, Mar 27 '10 at 16:47
You can set up a loop that goes over the array that DOMDocument::getElementsByTagName('li') returns, and extract the data using the above method IF (class == "zk_list_c2 f_l") — Powertieke, Mar 27 '10 at 17:05

regular expression tog et values of html tag attributes

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