Local hosted API not accessible from Angular 4 http - php

Question

I've got a very strange issue.
local hosted PHP Slim App using XAMPP (localhost:4040)
local hosted Angular 4 App using CLI (localhost:4200)
Making API Requests using "Postman" and browser is no problem, everything works fine.
Now I'm integrating the requests into my Angular app using import { Headers, Http } from '#angular/http'; and observables.
const requestUrl = 'http://localhost:4040/register';
const headers = new Headers({
'content-type': 'application/x-www-form-urlencoded'
});
this.http
.get(requestUrl, {headers: headers})
.map(response => response.json())
.subscribe(result => {
console.log(result);
}, error => {
console.log(error);
});
The request always fails with:
Failed to load http://localhost:4040/register: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:4200' is therefore not allowed access.
But: I am definitely sending these headers!
public static function createJsonResponseWithHeaders($response, $requestedData)
{
// Add origin header
$response = $response->withHeader('Access-Control-Allow-Origin', '*');
$response = $response->withHeader('Access-Control-Allow-Methods', 'GET');
// Add json response and gzip compression header to response and compress content
$response = $response->withHeader('Content-type', 'application/json; charset=utf-8');
$response = $response->withHeader('Content-Encoding', 'gzip');
$requestedData = json_encode($requestedData, JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES | JSON_NUMERIC_CHECK | JSON_PRETTY_PRINT);
$response->getBody()->write(gzencode($requestedData), 9);
if (!$requestedData || (count($requestedData) === 0)) {
return $response->withStatus(404)->write('Requested data not found or empty! ErrorCode: 011017');
}
return $response;
}
What I already tried for solving:
Run Slim App inside a Docker Container to get a different origin than localhost - same behaviour
Add allow-origin-header right on top of the index.php
header('Access-Control-Allow-Origin: *'); - same behaviour

Answer 1

Your requests are blocked because of CORS not being set up properly. There are other questions that address this, e.g. How to make CORS enabled requests in Angular 2
What you should ideally look at using is a proxy that forwards your requests to the API, the latest Angular CLI comes with support for a dev proxy (see https://github.com/angular/angular-cli/blob/master/docs/documentation/stories/proxy.md) out of the box. You set it up with a proxy.conf.json that could look like this:
{
"/api": {
"target": "http://localhost:4040",
"secure": false,
"pathRewrite": {"^/api" : ""}
}
}
What this piece of code does is any requests from Angular to a URI matching /api will be forwarded to localhost:4040.
Note that you will also need to figure out how your app will talk to the API server in a non-dev environment. I have been happy with using Nginx to serve Angular files, and act as proxy for the API.

Answer 2

Sorry, my bad. The solution is simple:
The "Cache-control" header in the request seems to be not allowed, although it worked fine when testing the api with Postman.
I removed the header from the request and everything worked well.