<?php
$content = <<<HTML
<p>{wrapper btnlabel="AAA"}zzzzzzzzzzzzzzzzzzzz{/wrapper}</p>
<p>{wrapper btnlabel="Text"}</p>
<table>
<tbody>
<tr>
<th scope="row">123</th>
<td>1 123</td>
<td>12 123</td>
<td>3 123</td>
<td>1 123 123</td>
</tr>
<tr>
<th scope="row">123</th>
<td>2700 123.</td>
<td>1800 123.</td>
<td>1000 123.</td>
<td>300 123.</td>
</tr>
</tbody>
</table>
<p>{/wrapper}</p>
HTML;
preg_match_all('#(?>{wrapper btnlabel=(?>"|")(.+?)(?>"|")})(.*?){/wrapper}#s', $content, $matches);
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