CURL: not fetching url with unicode characters

Question

I'm using CURL to fetch a Yahoo! BOSS api url with a unicode query, but I'm getting an "bad request" error.

http://boss.yahooapis.com/ysearch/web/v1/கமல்ஹாசன்?appid={appid}&format=xml

The above url works fine and returns results in firefox.

Please could anybody help me to fix this.

$url = "http://boss.yahooapis.com/ysearch/web/v1/கமல்ஹாசன்?appid={appid}&format=xml";

$ch - curl_init($url);
curl_setopt($ch, CURLOPT_HEADER, true);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

$data = curl_exec($ch);

curl_close($ch);