$re = '~{{\*(\w+)}}(.+?){{/\w+}}~s';
$str = '<table>
<tbody>
<tr>
<th>Trainee</th>
<th>Status</th>
<th>Invited</th>
<th>Score</th>
<th>Action</th>
</tr>
{{*Trainees}}
<tr>
<td>{{display_name}}</td>
<td>{{status}}</td>
<td>{{invited_date}}</td>
<td>{{percentage}}</td>
<td>Some action button</td>
</tr>
{{/Trainees}}
</tbody>
</table>';
preg_match_all($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