in PHP, how to remove specific class from html tag?

Question

given the following string in PHP:

$html = \"

text 1


        
      

Answer 1

The DOMDocument class is a very straight-forward and easy-to-understand interface designed to assist you in working with your data in a DOM-like fashion. Querying your DOM with xpath selectors should be the task(s) all the more trivial:

Clear All Classes

// Build our DOMDocument, and load our HTML
$doc = new DOMDocument();
$doc->loadHTML($html);

// Preserve a reference to our DIV container
$div = $doc->getElementsByTagName("div")->item(0);

// New-up an instance of our DOMXPath class
$xpath = new DOMXPath($doc);

// Find all elements whose class attribute has test2
$elements = $xpath->query("//*[contains(@class,'test2')]");

// Cycle over each, remove attribute 'class'
foreach ($elements as $element) {
    // Empty out the class attribute value
    $element->attributes->getNamedItem("class")->nodeValue = '';
    // Or remove the attribute entirely
    // $element->removeAttribute("class");
}

// Output the HTML of our container
echo $doc->saveHTML($div);