PHP DOMXPath - Can't target the right node

Question

I know this is probably covered in other threads, but I've been searching all over StackOverflow and tried many solutions, this is why I'm asking.

With this html:

<div class="someclass">
<table>
    <tbody>
        <tr>
            <th class="state">Status</th>
            <th class="name">Name</th>
            <th class="type">Type</th>
            <th class="length">Length</th>
            <th class="height">Height</th>
        </tr>
        <tr>
            <td class="state state2"></td>
            <td class="name"></td>
            <td class="type t18"></td>
            <td class="length">2000 m</td>
            <td class="height"></td>
        </tr>
        <tr>
            <td class="state state1"></td>
            <td class="name"></td>
            <td class="type t18"></td>
            <td class="length">2250 m</td>
            <td class="height"></td>
        </tr>
        <tr>
            <td class="state state1"></td>
            <td class="name"></td>
            <td class="type t18"></td>
            <td class="length">3000 m</td>
            <td class="height"></td>
        </tr>
        <tr>
            <td class="state state2"></td>
            <td class="name"></td>
            <td class="type t18"></td>
            <td class="length">2250 m</td>
            <td class="height"></td>
        </tr>
    </tbody>
</table>
</div>

Now, this is the PHP code I have so far :

$dom = new DOMDocument();
$dom->loadHtmlFile('http://www.whatever.com');
$dom->preserveWhiteSpace = false;

$xp = new DOMXPath($dom);
$col = $xp->query('//td[contains(@class, "state1") and (contains(@class, "state"))]');
$length = 0;

foreach( $col as $n ) {
    $parent = $n->parentNode;
    $length += $parent->childNodes->item(3)->nodeValue; 
}
echo 'Length: ' . $length;

I need to:

1.- Sum the 'length' values so I can echo them, getting rid of the ' m' substring of the given values.

2.- Understand why I'm getting wrong the 'parentNodes', 'childNodes' and 'item()' parts. With many tries I've gotten 'Length: 0'

I know this isn't the place to get a full detailed explanation, but it is really hard to find tutorials targetting these concrete issues. It would be great if someone could give some advice on where I can get this information.

Thanks very much in advance.

Edited the 'Concat' part for simplicity.

Answer 1

Navigation through DOMDocument for a specified childNode value by using DOMXpath

function getInt($string)
{
    preg_match("/[0-9]+/i", $string, $val);

    $out = 0;
    if (isset($val) && !empty($val))
    {
        $out = $val[0];
    }

    return intval($out);
}

$dom = new DOMDocument();
$dom->loadHtml($html);
$dom->preserveWhiteSpace = false;

$xp = new DOMXPath($dom);
$length = 0;

foreach($xp->query('//td[@class="state state1"]/following-sibling::*[3]') as $element)
{
    $value = $element->nodeValue;
    $length += getInt($value);
}


echo $length;