$re = '/(?-is:<li style=|(?!\A)\G).*?\K(?i)(\b[a-z]{12,}\b)/m';
$str = '<div class=“right”>
<ol>
<li style=“padding: 0px; list-style-type: decimal; list-style-image: none; list-style-position: outside; font-family: “verdana”; font-size: 18px; color: black;”><div class=“marginleft”>Haemorrhoids <br>- piles</div></li>
<li style=“padding: 0px; list-style-type: decimal; list-style-image: none; list-style-position: outside; font-family: “verdana”; font-size: 18px; color: black;”><div class=“marginleft”>Haemorrhoids<br>-piles</div></li>
<li style=“padding: 0px; list-style-type: decimal; list-style-image: none; list-style-position: outside; font-family: “verdana”; font-size: 18px; color: black;”><div class=“marginleft”>Offensive haemorrhages</div></li>
<li style=“padding: 0px; list-style-type: decimal; list-style-image: none; list-style-position: outside; font-family: “verdana”; font-size: 18px; color: black;”><div class=“marginleft”>CONSCIOUSNESS of womb. Hysterically inclined.</div></li>
</ol>';
preg_match_all($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