html parsing with php DOMDocument

i'm trying to extract contents from a forum, I want to get all the topics links if the topic has more than one page, this is the topic format:

<td align="left">
<div class="topicos">
<a href="/_t_1593901" title="Welcome2">
<span class="titulo">
Hello World!
</span>
</a><br>
</div>
</td>

and this is the topic format if it has more then one page:

<td align="left">
<div class="topicos">
<a href="_t_1594517" title="Welcome">
<span class="titulo">
Hello World!
</span>
</a><br>
</div>
<span class="quickPaging">
[<img src="http://forum.imguol.com//forum/themes/jogos/images/clear.gif" class="master-sprite sprite-icon-minipost" alt="Ir à página" title="Ir à página">
Ir à página:
<a href="/_t_1594517?&amp;page=1">1</a>,&nbsp;
<a href="/_t_1594517?&amp;page=2">2</a>,&nbsp;
<a href="/_t_1594517?&amp;page=3">3</a>,&nbsp;
<a href="/_t_1594517?&amp;page=4开发者_高级运维">4</a>,&nbsp;
<a href="/_t_1594517?&amp;page=5">5</a>&nbsp;
]</span>
</td>

I want to get the id(_t_1594517) of those topics with 5 or more pages, how can I do that ? This is what I were tyring, but I got lost and I didn't understand the DOMDocument documentation very well, I'm new to programming and PHP, help:

<?php
$html = new DOMDocument();
$url = "http://website.com/forum/?page=";
$page = "1";
while($page <= 10)
{
$html->loadHTML($url + $page);

foreach($html->getElementsByTagName('td') as $td)
{
    if($td->hasAttributes())
    {
        if($td->getAttribute('align') == "left")
        {
            $div = $td->getElementsByTagName('div');
            if($div->hasAttributes())
            {
                if($td->getAttribute('class') == "topicos")
                {
                    $a = $td->getElementsByTagName('a');
                    {
                        if($a->hasAttributes())
                        {
                            /*$return['link'][] =*/ echo $a->getElementById('href')->tagName;
                        }
                    }
                }
            }
        }
    }
}   
}
?>

I think xpath can help you:

If $with_links had the HTML content with the 5 links then

$doc = new DOMDocument();
$doc->loadHTML($with_links);
$xpath = new DOMXPath($doc);

$quick_paging_links = $xpath->query('//span[@class="quickPaging"]/a[contains(@href,"_t_")]/@href');
if($quick_paging_links->length>4)
{
  $first_href = $quick_paging_links->item(0)->value;
  $id = substr($first_href, 1, strpos($first_href, '?')-1);
  echo 'Topic with id '.$id.' has '.$quick_paging_links->length." links.\n";
}

will produce the output:

Topic with id _t_1594517 has 5 links.