Wrapper class returns null

Question

public class facebookuser{
    public String id;   //115020323424341
    public String name; //XXXX
    public cls_picture picture;
    public String birthday; //09/12/1990
    public String about;    //I beleive
    public class cls_picture {
        public cls_data data;
    }
    public class cls_data {
        public boolean is_silhouette;
        public String url; 
    }
    public static facebookuser parse(String json){
        return (facebookuser) System.JSON.deserialize(json, facebookuser.class);
    }
}

global class facebook_call
{
     public static String getownprofile(String token)
     {
            Boolean flag =false;
            Http http =new Http();
            HttpRequest req =new HttpRequest();
            req.setEndpoint('https://graph.facebook.com/me?fields=id,name,picture,birthday,about&access_token='+token);
            req.setmethod('POST');
            HttpResponse res = http.send(req);             
           facebookuser objfacebookuser = new facebookuser();
           objfacebookuser=facebookuser.parse(res.getBody());
    } 

objfacebookuser is Null. why ? Do i need to set properties in default constructor ? Then How ?

beginner in APEX

 {
  "id": "112344322434",
"name": "XXXXXXXXXXXX",
"birthday": "09/12/1990",
"about": "I beleive.",
"picture": {
"data": {
  "is_silhouette": false,
  "url": "https://scontent.xx.fbcdn.net/v/t1.0-1/p50x50/13658929_1039496126116440_8074761312212223685568213_n.jpg?oh=24a1c83a6417dd176bc5c134637a0d1b&oe=58B47A02"
 }
}
}

debug log

16:26:58:430 USER_DEBUG [54]|DEBUG|facebookuser:[about=null, birthday=null, id=null, name=null, picture=null]

Answer 1

Make the request as GET Method It will return perfect output.