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Grep... What patterns to extract href attributes, etc. with PHP's preg_grep?

Answer 1

+3 A:

First of all, you should not use regex to extract data from an HTML string.
Instead, you should use a DOM Parser !

Here, you could use :

DOMDocument::loadHTML to load the HTML string
- eventually, using the @ operator to silence warnings, as your HTML is not quite valid.
The DOMXPath class to do XPath queries on the document
DOM methods to work on the results of the query
- See the classes in the Document Object Model section of the manual, and their methods.

For example, you could load your document, and instanciate the DOMXpath class this way :

$html = <<<HTML
....
....
HTML;

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

$xpath = new DOMXPath($dom);

And, then, use XPath to find the elements you are looking for.

For example, in the first case, you could use something like this, to find all <a> tags that are children of <h2> tags :

// <h2><a ....>_____</a></h2>
$tags = $xpath->query('//h2/a');
foreach ($tags as $tag) {
    var_dump($tag->nodeValue);
}
echo '<hr />';

Then, for the second and third case, you are searching for <a> tags that are children of <cite> tags -- and when you've found them, you want to check if they have a href attribute or not :

// <cite><a href="_____" .... >...</a></cite>
// <cite><a .... >________</a></cite>
$tags = $xpath->query('//cite/a');
foreach ($tags as $tag) {
    if ($tag->hasAttribute('href')) {
        var_dump($tag->getAttribute('href'));
    } else {
        var_dump($tag->nodeValue);
    }
}
echo '<hr />';

And, finally, for the last one, you just want <span> tags :

// <span>_________</span>
$tags = $xpath->query('//span');
foreach ($tags as $tag) {
    var_dump($tag->nodeValue);
}

Not that hard -- and much easier to read that regexes, isn't it ? ;-)

Pascal MARTIN 2010-04-03 11:56:40

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Grep... What patterns to extract href attributes, etc. with PHP's preg_grep?

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