将div连接成报废内容

I'm using PHP simple dom parser, how should I insert extra entities within them? like $html contain

<table class="tb">..</table>
<table>..</table>
<table>..</table>

I know how to select the dom, like $html->find('div[class="tb"][1]'); but how to concatenate new div after it? like I want to put ads btw table.

if you still want simpledom example:

$banner = '<div class="ads">blablabla</div>';
$tables = $html->find('table');
foreach($tables as $table){
    $table->outertext .= $banner;
}

OR:

$html->find('div[class="tb"][1]').outertext .= '<div class="ads">blablabla</div>';

made after reading docs from here (: