XML parsing error while using CURL extension

I am working in yii framework. I am using curl extension. i had included code in main.php as-

'curl'=>array(
    'class' => 'application.extensions.curl.Curl',
    ),

And included curl.php file under protected/extensions. In controller i had included code as=

public function actionGetWeather()
{
    $place='pune';
    $data = Yii::app()->curl->run('http://www.google.com/ig/api?weather='.$place.'&hl=en');

$xml = new SimplexmlElement($data);
foreach($xml->weather as $item) {

    foreach($item->current_conditions as $new) {

        //For temperature in fahrenheit replace temp_c by temp_f
        $current_temperature=$new->temp_c['data'];
        $current_humidity=$new->humidity['data'];
    }

    $current_condition=$item->forecast_conditions[0]->condition['data'];
    $next_temperature=$item->forecast_conditions[1]->high['data'];

    //to convert Fahrenheit into Celcius
    $next_temperature=round(($next_temperature-32)*(5/9));

    $next_condition=$item->forecast_conditions[1]->condition['data'];
}

echo " Current temperature :".$current_temperature."<br />";
echo "Current condition : ".$current_condition."<br />";
echo $current_humidity;
echo "Tomorrows temperature :".$next_temperature."<br />";
echo "Tomorrows condition : ".$next_condition."<br />";
}

But its giving an error as String could not be parsed as XML at line "$xml = new SimplexmlElement($data);" So what changes i need to make? please help me