android发送的json数据 后台php的接收代码要怎么写呢

[狭路相逢萌者胜]

public class MainActivityF extends Activity {
private TextView tv;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tv = (TextView) findViewById(R.id.tv);
KJHttp kjh = new KJHttp();
HttpParams params = new HttpParams();

JSONObject jsonObject = new JSONObject();
try {
jsonObject.put("a", "nihao");
jsonObject.put("b", "123456");
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
params.putJsonParams(jsonObject.toString());
HttpCallBack callBack = new HttpCallBack() {
@Override
public void onSuccess(String t) {
// TODO Auto-generated method stub
super.onSuccess(t);
Toast.makeText(MainActivityF.this,"hello", Toast.LENGTH_SHORT).show();
tv.setText(t);
}
@Override
public void onFailure(int errorNo, String strMsg) {
// TODO Auto-generated method stub
super.onFailure(errorNo, strMsg);
tv.setText(strMsg);
}
};
kjh.jsonPost("http://192.168.1.170:8888/test.php",params,callBack);

kjh.removeCache("http://192.168.1.170:8888/test.php");

}
}

[狭路相逢萌者胜]

后台连接成功了 但是 得不到我所发送的变量 所以后台要怎么改呢 php不是很懂 希望大牛指点