$re = '/<table\b[^\>]*\bname=(\"|\')?table01\1[^\>]*>(?>([^\<]+|<(?!\/?table\b))|(<table[^\>]*>(?:(?2)|(?3)|)+?<\/table>))*<\/table>/ix';
$str = '<table name="table01" data-measure-unit="Y">
<table></table>
</table>
<table name="table01" data-measure-unit="Y">
<div>
<table></table>
</div>
</table>
<table name="table01" data-measure-unit="Y">
<div>
<table>
<table>
</table>
</table>
</div>
</table>
<table name="table01" data-measure-unit="Y">
<div>
<div></div>
</div>
</table>
<table name="table01" data-measure-unit="Y">
</table>
<table name="table01"></table>';
preg_match_all($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