Help JSON api coding data pullout


Hello, can anyone help with this code, i’m trying to pullout data from the other website using JSON api, Can anyone spot the problem with the code?

 $goods_sn = 'DDFF0001';
//$goods_sn = array('DDFF0001','DDFF0002');
//$goods_sn = 'DDFF0001,DDFF0002';
$post_data = array(
'token' => 'your access token',
'goods_sn' => json_encode($goods_sn)
$curl = curl_init($api_url);
 curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, 1);
 curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($curl, CURLOPT_POST, 1);
curl_setopt($curl, CURLOPT_POSTFIELDS, $post_data);
$result = curl_exec($curl);

There is no $post_data defined in what you posted.