Angular 4 POST call to php API fails, but GET requ

问题:

I have an Angular 5 application which connects to an PHP API, everything worked ok when testing in local environment (Ubuntu 16.04, Apache2 2.4.18, PHP 7.2.2) but when I deployed the project in my school server (Uubuntu, Apache2 2.4.27, PHP 7.1.11), GET requests are ok but POST requests are turned into OPTIONS requests and Angular displays the error.

ERROR Object { _body: error, status: 0, ok: false, statusText: "", headers: {…}, type: 3, url: null }

Request from origin has been blocked from loading by Cross-Origin Resource Sharing policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.

I have alredy tested the API with Postman and everything works.

Here is the code of the DataService

constructor(public http:Http) {
  this.url = 'http://10.50.67.83/usuario1/Autozone/';
  this.headers = new Headers();
  this.headers.append('Content-Type', 'application/json');
}

postRequisition(client:string, cart:Selected[]) {
  let data:Data;
  data = {client: client, cart: cart};

  return this.http.post(
    this.url + 'api/requisitions/create.php',
    JSON.stringify(data),
  {
    method: 'POST',
    headers: this.headers
  }).map(res => res.json());
}

I have added the ContentType header beacause I'm posting a JSON.

These are the headers included in the php file.

header("Access-Control-Allow-Origin: *");
header("Access-Control-Allow-Methods: POST");
header("Access-Control-Allow-Headers: Content-Type");
header("Content-Type: application/json; charset=UTF-8");
header("Accept: application/json;");