$re = '/<(\w*)>([\S\s]*?)<\/\1>/ms';
$str = '<blockquote> This is a blockquote with two paragraphs. Lorem ipsum dolor sit amet,
consectetuer adipiscing elit. Aliquam hendrerit mi posuere lectus.
Vestibulum enim wisi, viverra nec, fringilla in, laoreet vitae, risus.
Donec sit amet nisl. Aliquam semper ipsum sit amet velit. Suspendisse
id sem consectetuer libero luctus adipiscing.</blockquote>
<blockquote> This is the first level of quoting.
<blockquote> This is nested blockquote.</blockquote>
Back to the first level.</blockquote>
<div>
Not nested
</div>
<div>
Top level
<div>Nested</div>
</div>';
preg_match_all($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