PHP: How to find <div and /div in a string?

I pass an array of html code to a php function with the intention of extracting and returning a subset of it.

Here's a partial example of the data passed in:

[0] => <div class="positionIs" style="float:right;width:181px;">
[1] => <table class="datab" style="width:100%;">
[2] => <tr>
[3] => <th colspan="2" style="padding:4px;">Position ist...
[4] => </th>
[5] => </tr>
[6] => <tr class="hell">  
[7] => <td style="text-align:left;">...tats&auml;chliche Position
[8] => </td>
[9] => <td style="font-weight:bold;padding:2px;">
[10] => <div style="text-align: center;border:1px solid black;padding:1px;height:1.4em;width:1.4em;background-color:#ffffff;">
[11] => </div>

To return, e.g. the first table row ([2] - [5]) it seems to me that I need to test for "

I've tried to do it with strpos, but it just doesn't work as I expect it to. That's probably because of the presence of the "<" and "/" in the strings. I've tried escaping it with a backslash but that didn't work either. How should I test these strings?

As requested below, here's the code from my function:

$str_out = '';
$tracker = 0;
$start = '<tr';
$end = '/tr';
for ($i = 0, $ii = count($arr_in); $i < $ii; $i++)
{
    $str_out .= $arr_in[$i];
    if (strpos($arr_in[$i], $start) === true)
    {
        $tracker++;
    }
    if (strpos($arr_in[$i], $end) === true)
    {
        $tracker--;
    }
    if (!$tracker) break;
}

Solution

strpos won't return TRUE. It will return the position the first character of the 'needle' is found or return FALSE if it has not been found. For more info check the manual here: http://php.net/manual/en/function.strpos.php

So instead of using

if (strpos($arr_in[$i], $start) === true)

you can check for non-false like this:

if (strpos($arr_in[$i], $start) !== false)