Hide This – Easy Fix for 2.5?

The Hide This plugin (https://edwards.org/2006/03/12/hidethis-v10-plugin-for-wordpress) does exactly what i need but it doesn’t seem to work with 2.5

The code is pretty simple (<20 lines) and I’m wondering if there is a quick fix to get it to work in 2.5

add_filter('the_content', 'hide_some_content');

function hide_some_content($content) {
global $current_user, $user_ID;

if (($current_user->id == 0) && ($user_ID == 0)){

	$b = strpos($content, '<!--hidethis-->');
	$e = strpos($content, '<!--/hidethis-->');

	$pre = substr($content,0,$b);
	$suf .= substr($content,$e,strlen($content));

	return $pre.$suf;

} else { return $content; }

}

Thanks in advance.