In order to get the number of followers of a user you have to:
1.) create a SoundCloud application: http://soundcloud.com/you/apps
2.) use this code in your website (and replace {$user_id} with your username, replace {$client_id} with the application’s Client id – displayed after you create the application):

$sc_content = file_get_contents("http://api.soundcloud.com/users/{$user_id}?consumer_key={$client_id}");
$sc_xml = simplexml_load_string($sc_content);

echo $sc_xml -> {‘followers-count’};

And that’s all!