imageshack API cURL - post

Question

I now the credentials are correct.
When I send a image through Form like this:(action="http://api.imageshack.com/v2/images/").
Its working fine but When I tried to send $ch = curl_init($url);
Its failed.
CODE:
enter code here
<form action="" method="post" enctype="multipart/form-data">
Select image to upload:
<input type="file" name="file" id="file" multiple>
<input type="text" name="auth_token" id="auth_token" value="xxxxxxxxxxxxxxxx">
<input type="text" name="api_key" id="api_key" value="xxxxxxxxxxxxxxx">
<input type="submit" value="Upload Image" >
</form>
$url = 'http://api.imageshack.com/v2/images/';
$temp = $_FILES["file"]['tmp_name'];
echo $temp."<br>" ;
$ch = curl_init($url);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_TIMEOUT, 240);
curl_setopt($ch, CURLOPT_POSTFIELDS, array(
'file'=> '#'.$temp,
"key" => "xxxxxxxxxxxxxxxxxxxx",
"auth_token" => "xxxxxxxxxxxxxxx"
));
curl_exec($ch);
I have also tried with Header: curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
And i get error from imageshack as json: {"error_code":1,"error_message":"Invalid image file. The file uploaded is not being detected as an image file.","error_info":{"Content-Type":null,"filesize":0}}