<?php
$doc = new DOMDocument();
$string = '<!DOCTYPE html>
<html lang="fr">
<head>
<meta http-equiv="content-type" content="text/html" />
<title>test</title>
</head>
<body>
    <div class="List">
        <span class="bold">foo</span>
        <span class="bold">bar</span>
        <span class="bold">base</span>
    </div>
</body>
</html>
';

// You can use a local or a HTTP file :
//$doc->loadHTMLFile();
// or a string:
$doc->loadHTML($string);

$xpath = new DOMXpath($doc);

$elements = $xpath->query('//span[@class="bold"]');

if (!is_null($elements)) {
    foreach ($elements as $element) {
        $nodes = $element->childNodes;
        foreach ($nodes as $node) {
            echo $node->nodeValue. "\n";
        }
    }
}
?>