Angular 4 CLI - Get the response from a PHP file?

How do I get the response from a PHP file in Angular 4?

If i place the PHP file in the assets folder, the GET request will find the file and it will download the content of the file. E.g

headers: Headers
ok: true
status: 200
statusText: "OK"
type: 2
url: "http://localhost:4200/assets/php/test.php"
_body: "<?php ↵    echo 'response from php file';↵?>"

Also if I browse localhost:4200/assets/test.php it will donwload the php file to disk.

If I place the file in the same service folder and try to call it with ./test.php I get the 404 file not found error. I also get the 404 error if I try to target the file with the full path name like './app/services/test.php' (I've tried a few other variants aswell)

test.service.ts

import { Injectable } from '@angular/core';
import { Http, Response } from '@angular/http';

@Injectable()
export class TestService {

  data: any;

  constructor(private _http: Http) { }

  getTestData() {
    return this._http.get('assets/php/test.php') // <-- Here
      .subscribe(
      (res: Response) => {
        this.data = res;
        console.log(this.data)
      },
      (err: Error) => console.log(err)
      );
  }
}

home.component.ts

import { Component, OnInit } from '@angular/core';
import { TestService } from '../services/test.service';

@Component({
  selector: 'app-home',
  templateUrl: './home.component.html',
  styleUrls: ['./home.component.css']
})
export class HomeComponent implements OnInit {

  data: any;

  constructor(private _testService: TestService) {}

  ngOnInit() {
     this.data = this._testService.getTestData();
     console.log(this.data);
  }
}

test.php

<?php
   echo 'response from php file';
?>

app.moduel.ts

import { TestService } from './services/test.service';
...
providers: [TestService],

Project structure