使用Yahoo Weather feed的自定义图像

I'm retrieving data from Yahoo Weather currently and able to display the elements I need so far. I'm stumped on how to use the Condition Codes (i think i need to turn the number into an integer) to have a string such that I can display my own custom icons. As the weather in the region I am tracking is fairly mild I want to assign only a small number of icons but have each cover a string of Condition Codes. So far this is my code that is working–

function bm_getWeather ($code = '', $temp = 'c') {

$file = 'http://weather.yahooapis.com/forecastrss?w=' . $code . '&u=' . $temp;

$request = new WP_Http;
$result = $request->request($file);

if (isset($result->errors)) {
    return FALSE;
}

$data = $result['body'];

$output = array (
    'temperature' => bm_getWeatherProperties('temp', $data),
    'weather_code' => bm_getWeatherProperties('code', $data),
    'class' =>  bm_getWeatherProperties('code', $data),
    'weather' => bm_getWeatherProperties('text', $data),        
);

return $output;

}

function weather_icon() {

$data = bm_getWeather($code = '', $temp = 'c');

// Error is here
$nums = (int)$data['weather_code']; // Needs to be cast as an integer

$severe = array(12, 13, 14, 16, 19);
$rain = array(3200);

// Therefore the maths is wrong
switch($nums) {
    case (in_array($nums, $severe)):
        $cat = 'severe';
    break;
    case (in_array($nums,$rain)):
        $cat = 'snow';
    break;
    default:
        $cat = 'happy';
    break;

}
return $cat;

}

function bm_getWeatherProperties ($needle, $data) {

$regex = '<yweather:condition.*' . $needle . '="(.*?)".*/>';
preg_match($regex, $data, $matches);

return (string)$matches[1];

}

Any help would be much appreciated as my php skills are less than adequate right now.