$content gives the html code like:
<p>text</p>
<p><img ... /></p>
<div class="video">...</div>
or just
<p>text</p>
<p>more text</p>
Also we have a variable:
$video_match = false;
We should turn $video_match to true, if <div class="video"> (exactly this code) exists in $content.
Thanks.