$re = '/<div.*?>(.*?)<\/div>/s';
$str = '<div id="_mcePaste">
<ul>
<li> Computer is stolen </li>
<li> Someone else has gained access to your certificate </li>
<li> Employee leaves or transfers to another department </li>
<li> Certificate is corrupted </li>
</ul>
Links:
<p>http://customs.gov.au/webdata/resources/files/digital_certificate_and_client_registrations.pdf</p>
<p></p>
</div>';
$subst = "\1";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
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