Why is that my data is not storing in the database even though i have successfully authenticated an account

Im having trouble with this why is the data is not storing in my database but i successfully registered and sign in where the hell my data goes ?

dbconnect.php

<?php

  define('HOST','localhost');
  define('USER','root');
  define('PASS','');
  define('DB','ionicdon_maindb');

  $con = mysqli_connect(HOST,USER,PASS,DB);
   if (!$con){
     die("Error in connection" . mysqli_connect_error()) ;
  }
?>

im having trouble with this why is the data is not storing in my database but i successfully registered and sign in where the hell my data goes ?

dbconnect.php

<?php

  define('HOST','localhost');
  define('USER','root');
  define('PASS','');
  define('DB','ionicdon_maindb');

  $con = mysqli_connect(HOST,USER,PASS,DB);
   if (!$con){
     die("Error in connection" . mysqli_connect_error()) ;
  }
?>

this is the registration i only just copy this code from this link [https://ionicdon.com/setup-login-register-ionic3-using-php-mysql/?unapproved=6226&moderation-hash=40109fbea56e53ddf7b4fb4f654031ff#comment-6226]

register.ts

import { Component, ViewChild } from '@angular/core';
import { IonicPage, NavController, NavParams, AlertController } from 'ionic- 
angular';
import { LoginPage } from '../login/login';
import { Http, Headers, RequestOptions }  from "@angular/http";
import { LoadingController } from 'ionic-angular';
import 'rxjs/add/operator/map';

@IonicPage()
@Component({
  selector: 'page-register',
  templateUrl: 'register.html',
})
export class RegisterPage {

  @ViewChild("email") email;
  @ViewChild("username") username;
  @ViewChild("mobile") mobile;
  @ViewChild("password") password;

  constructor(public navCtrl: NavController, public navParams: NavParams, 
 public alertCtrl: AlertController,
              private http: Http,  public loading: LoadingController) {
  }

  ionViewDidLoad() {
    console.log('ionViewDidLoad RegisterPage');
  }

  Register(){

  if(this.username.value=="" ){
    let alert = this.alertCtrl.create({
      title:"ATTENTION",
      subTitle:"Username field is empty",
      buttons: ['OK']
    });
      alert.present();
    }

  else
    if(this.email.value==""){
    let alert = this.alertCtrl.create({
      title:"ATTENTION",
      subTitle:"Email field is empty",
      buttons: ['OK']
    });
      alert.present();
    }

  else
    if(this.mobile.value=="" ){
    let alert = this.alertCtrl.create({
      title:"ATTENTION",
      subTitle:"Mobile number field is empty",
      buttons: ['OK']
    });
      alert.present();
    }

  else
    if(this.password.value==""){
    let alert = this.alertCtrl.create({
      title:"ATTENTION",
      subTitle:"Password field is empty",
      buttons: ['OK']
    });
      alert.present();
    }

  else{
    var headers = new Headers();
    headers.append("Accept", 'application/json');
    headers.append('Content-Type', 'application/json' );
    let options = new RequestOptions({ headers: headers });
    let data = {
      username: this.username.value,
      password: this.password.value,
      mobile: this.mobile.value,
      email: this.email.value
    };

    let loader = this.loading.create({
      content: 'Processing please wait…',
    });

  loader.present().then(() => {
    this.http.post('http://ionicdon.com/mobile/register.php', data, options)
      .map(res => res.json())
      .subscribe(res => {
        loader.dismiss()

        if(res=="Registration successfull"){
          let alert = this.alertCtrl.create({
          title:"CONGRATS",
          subTitle:(res),
          buttons: ['OK']
          });
          alert.present();
          this.navCtrl.push(LoginPage);
          }

        else{
          let alert = this.alertCtrl.create({
            title:"ERROR",
            subTitle:(res),
            buttons: ['OK']
            });
              alert.present();
          }
        });
      });
    }
  }

}