$re = '/(?:<iepigraph(?U).*>(?-U)(?:\s)*)+(?U)(.*)(?-U)(?:<\/iepigraph>)+/m';
$str = '<p class="p">Del podio del último Balón de Oro sólo sigue él en el Mundial y demostrando que es un crack absoluto.</p>
<p>
<b>
<span class="p">
<iepigraph class="epitit">
<iepigraph class="epitit">2. REGATE</iepigraph>
</iepigraph>
</span>
</b>
<span class="p"/>';
preg_match_all($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