使用xpath和php从html页面检索数据

I know there are similar question, but, trying to study PHP I met this error and I want understand why this occurs.

<?php
    $url = 'http://aice.anie.it/quotazione-lme-rame/';
    echo "hello!
";
    $html = new DOMDocument();
    @$html->loadHTML($url);
    $xpath = new DOMXPath($html);
    $nodelist = $xpath->query(".//*[@id='table33']/tbody/tr[2]/td[3]/b");

    foreach ($nodelist as $n) {
        echo $n->nodeValue . "
";
    }
?>

this prints just "hello!". I want to print the value extracted with the xpath, but the last echo doesn't do anything.

You have some errors in your code :

1. You try to get the table from the url http://aice.anie.it/quotazione-lme-rame/, but it's actually in an iframe located at http://www.aiceweb.it/it/frame_rame.asp, so get the iframe url directly.

2. You use the function loadHTML(), which load an HTML string. What you need is the loadHTMLFile function, which takes the link of an HTML document as a parameter (See http://www.php.net/manual/fr/domdocument.loadhtmlfile.php)

3. You assume there is a tbody element on the page but there is no one. So remove that from your query filter.

Working code :

$url = 'http://www.aiceweb.it/it/frame_rame.asp';
echo "hello!
";
$html = new DOMDocument();
@$html->loadHTMLFile($url);
$xpath = new DOMXPath($html);
$nodelist = $xpath->query(".//*[@id='table33']/tr[2]/td[3]/b");

foreach ($nodelist as $n) {
    echo $n->nodeValue . "
";
}