RegEx to get the keywords from HTML

Question

I'm trying to obtain the keywords from an HTML page that I'm scraping with PHP.

So, if the keywords tag looks like this:

<meta name="Keywords" content="MacUpdate, Mac Software, Macintosh Software, Mac Games, Macintosh Games, Apple, Macintosh, Software, iphone, ipod, Games, Demos, Shareware, Freeware, MP3, audio, sound, macster, napster, macintel, universal binary">

I want to get this back:

MacUpdate, Mac Software, Macintosh Software, Mac Games, Macintosh Games, Apple, Macintosh, Software, iphone, ipod, Games, Demos, Shareware, Freeware, MP3, audio, sound, macster, napster, macintel, universal binary

I've constructed a regex, but it's not doing the trick.

(?i)^(<meta name=\"keywords\" content=\"(.*)\">)

Any ideas?

Answer 1

(?i)<meta\\s+name=\"keywords\"\\s+content=\"(.*?)\">

Would produce something like:

preg_match('~<meta\\s+name=\"keywords\"\\s+content=\"(.*?)\">~i', $html, &$matches);

Answer 2

This is a simple regex, that matches the first meta keywords tag. It only allows characters, numbers, legal URL characters, HTML entities and spaces to appear inside the content attribute.

$matches = array();
preg_match("/<meta name=\"Keywords\" content=\"([\w\d;,\.: %&#\/\\\\]*)\"/", $html, $matches);
echo $matches[1];

Answer 3

(.*) matches everything up to the LAST "(quote) in the document, obviously not what you want. Regex is greedy by default. You need to use

content=\"(.*?)\"

or

content=\"([^\"]*)\"

Answer 4

Use the function get_meta_tags();

Tutorial

Answer 5

I would use a HTML/XML parser like DOMDocument and XPath to retrieve the nodes from the DOM:

$doc = new DOMDocument();
$doc->loadHTML($html);
$xpath = new DOMXPath($doc);
$keywords = $xpath->query('//meta[translate(normalize-space(@name), "KEYWORDS", "keywords")="keywords"]/@content');
foreach ($keywords as $keyword) {
    echo $keyword->value;
}

The translate function seems to be necessary as PHP’s XPath implementation does not know the lower-case function.

Or you do the filtering with PHP:

$metas = $xpath->query('//meta');
foreach ($metas as $meta) {
    if ($meta->hasAttribute("name") && trim(strtolower($meta->getAttribute("name")))=='keywords' && $meta->hasAttribute("content")) {
        echo $meta->getAttribute("content")->value;
    }
}

Answer 6

Stop trying to parse HTMl with regular expressions.

http://stackoverflow.com/questions/1732348/regex-match-open-tags-except-xhtml-self-contained-tags/1732454#1732454