<?php
$html = <<<EOF
<table>
<thead>
<tr>
<th>Col 1</th>
<th>Col 2</th>
<th>Col 3</th>
<th>Col 4</th>
<th>Col 5</th>
<th>Col 6</th>
</tr>
</thead>
<tbody>
<tr>
<td>Conteudo 1</td>
<td>Conteudo 2</td>
<td>Conteudo 3</td>
<td>Conteudo 4</td>
<td>Conteudo 5</td>
<td>Conteudo 6</td>
</tr>
<tr>
<td>Conteudo 1</td>
<td>Conteudo 2</td>
<td>Conteudo 3</td>
<td>Conteudo 4</td>
<td>Conteudo 5</td>
<td>Conteudo 6</td>
</tr>
</tbody>
</table>
EOF;


// criar um novo documento 
$document = new DOMDocument();

// ler o html
$document->loadHTML($html);

// criar seletor xpath
$selector = new DOMXPath($document);

//selecionar conteudo das td's
$results = $selector->query('//td');

// resultado
foreach($results as $node) {
    echo $node->nodeValue . PHP_EOL;
}