$arr=explode("<code>", $html);
foreach ($arr as $current){
if (strpos($current, "</code>")===false){
echo $current;
} else {
$arr2=explode("</code>", $current);
echo "<blockquote class='phpcode'>";
highlight_string($arr2[0]);
echo "</blockquote>";
echo $arr2[1];
}
}