$re = '/>(?:\n|\r\n)/m';
$str = 'bla;bla<ul>
<li>line one</li>
<li>line one</li>
<ul>bla
line two
line tree';
$subst = ">";
$result = preg_replace($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