$re = '/.*?<tr>.*?<\/tr>.*?(<tr>).*?<\/tr>.*?/si';
$str = ' <tr>
<td style="height:24px; width:56px">0,8</td>
<td style="width:139px">10Х17Н13М2Т</td>
<td style="width:347px">1,0х2,0(8)</td>
<td style="width:103px">0,1</td>
</tr>
<tr>
<td style="height:24px">1</td>
<td>08кп</td>
<td>1,0х2,0</td>
<td>1,338</td>
</tr>
<tr>
<td style="height:24px; width:56px">0,8</td>
<td style="width:139px">10Х17Н13М2Т</td>
<td style="width:347px">1,0х2,0(8)</td>
<td style="width:103px">0,1</td>
</tr>
<tr>
<td style="height:24px">1</td>
<td>08кп</td>
<td>1,0х2,0</td>
<td>1,338</td>
</tr>';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php