Unable to send data on my database cant understand what is happening - php

Question

Getting this error
Code:
Post_providers.ts
import { Injectable } from '#angular/core';
import { Http, Headers, RequestOptions } from '#angular/http';
import 'rxjs/add/operator/map';
#Injectable()
export class PostProviders {
server: string = "http://localhost/server_api/"
constructor(public http: Http){
}
postData(body, file){
let type = "application/json; charset=UTF-8";
let headers = new Headers ({'Content-type': type});
let options = new RequestOptions({headers: headers});
return this.http.post(this.server + file, JSON.stringify(body), options)
.map(res => res.json());
}
}
file_aksi.php
import { Injectable } from '#angular/core';
import { Http, Headers, RequestOptions } from '#angular/http';
import 'rxjs/add/operator/map';
#Injectable()
export class PostProviders {
server: string = "http://localhost/server_api/"
constructor(public http: Http){
}
postData(body, file){
let type = "application/json; charset=UTF-8";
let headers = new Headers ({'Content-type': type});
let options = new RequestOptions({headers: headers});
return this.http.post(this.server + file, JSON.stringify(body), options)
.map(res => res.json());
}
}
config.php
define('Db_name', 'ionic_app');
define('Db_user', 'root');
define('Db_password', '');
define('Db_host', 'localhost');
$mysqli = new mysqli(Db_name, Db_host, Db_password, Db_user);
i have am still trying to solve this issue but still no luck. i am working to solve this error from last 2 days and don't understand that what is the thing which is not correctly done by me.
Error as written in comment by Farrukh iftikhar:
core.js:1448 ERROR SyntaxError:
Unexpected token d in JSON at position 0
at JSON.parse (<anonymous>)
at Response.Body.json (http.js:1091)
at MapSubscriber.project (post_providers.ts:20)
at MapSubscriber._next (map.js:79)
at MapSubscriber.Subscriber.next (Subscriber.js:89)
at XMLHttpRequest.onLoad (http.js:1591)
at t.invokeTask (polyfills.js:3)
at Object.onInvokeTask (core.js:4740)
at t.invokeTask (polyfills.js:3) at r.runTask (polyfills.js:3)