How can PHP parse HashMap data from android post request?

@Override
protected String doInBackground(String... params) {

     HashMap<String, String> data = new HashMap<String,String>();
     data.put("name",params[0]);
     data.put("username",params[1]);
     data.put("password",params[2]);
     data.put("email",params[3]);

     String result = ruc.sendPostRequest(REGISTER_URL,data);

     return  result;
}

Here is PHP codes:

if($_SERVER['REQUEST_METHOD']=='POST'){
    $name = $_POST['name'];
    $username = $_POST['username'];
    $password = $_POST['password'];
    $email = $_POST['email'];
}

How can php parse the HashMap?I am newbee,thanks for answers!