$re = '/(?m-s)^.*<div class="info">(?:.*\n){5}/';
$str = ' <div>
<div class="info">
line1
line2
line3
line4
line5
line6
';
$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