$re = '/(?=(@embed(?:(?>(?:(?!@embed|@endembed).)+)*|(?1))*@endembed))/s';
$str = '@extends(\'layouts/default\')
@section(\'content\')
<div class="row">
<div class="col-md-6">
@embed(\'components/box\')
@section(\'title\', \'Box title\')
@section(\'content\')
<h4>Haai</h4>
Box content
@stop
@endembed
</div>
<div class="col-md-6">
@embed(\'components/box\')
@section(\'title\', \'Box2 title\')
@section(\'content\')
@embed(\'components/timeline\')
@section(\'items\')
@stop
@endembed
@stop
@endembed
</div>
</div>
@stop';
preg_match_all($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