php怎么做api上传文件接口

$file = realpath('gif/1.gif'); //要上传的文件
$fields['f'] = '@'.$file;

$ch = curl_init();  
curl_setopt($ch, CURLOPT_URL,"你的api接口");  
curl_setopt($ch, CURLOPT_POST, 1 );
curl_setopt($ch, CURLOPT_POSTFIELDS, $fields);

curl_exec ($ch);  
curl_close ($ch);