Getting DOM elements by classname

If you wish to get the innerhtml of the class without the zend you could use this:

$dom = new DomDocument();
$dom->load($filePath);
$classname = 'main-article';
$finder = new DomXPath($dom);
$nodes = $finder->query("//*[contains(concat(' ', normalize-space(@class), ' '), ' $classname ')]");
$tmp_dom = new DOMDocument(); 
foreach ($nodes as $node) 
    {
    $tmp_dom->appendChild($tmp_dom->importNode($node,true));
    }
$innerHTML.=trim($tmp_dom->saveHTML()); 
echo $innerHTML;

Update: Xpath version of *[@class~='my-class'] css selector

So after my comment below in response to hakre's comment, I got curious and looked into the code behind Zend_Dom_Query. It looks like the above selector is compiled to the following xpath (untested):

[contains(concat(' ', normalize-space(@class), ' '), ' my-class ')]

So the PHP would be:

$dom = new DomDocument();
$dom->load($filePath);
$finder = new DomXPath($dom);
$classname="my-class";
$nodes = $finder->query("//*[contains(concat(' ', normalize-space(@class), ' '), ' $classname ')]");

Basically, all we do here is normalize the class attribute so that even a single class is bounded by spaces, and the complete class list is bounded in spaces. Then append the class we are searching for with a space. This way we are effectively looking for and find only instances of my-class .

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Use an xpath selector?

$dom = new DomDocument();
$dom->load($filePath);
$finder = new DomXPath($dom);
$classname="my-class";
$nodes = $finder->query("//*[contains(@class, '$classname')]");

If it is only ever one type of element you can replace the * with the particular tagname.

If you need to do a lot of this with very complex selector I would recommend Zend_Dom_Query which supports CSS selector syntax (a la jQuery):

$finder = new Zend_Dom_Query($html);
$classname = 'my-class';
$nodes = $finder->query("*[class~=\"$classname\"]");