[angular] How to add CORS request in header in Angular 5

please import requestoptions from angular cors

    import {RequestOptions, Request, Headers } from '@angular/http';

and add request options in your code like given below

    let requestOptions = new RequestOptions({ headers:null, withCredentials: 
    true });

send request option in your api request

code snippet below-

     let requestOptions = new RequestOptions({ headers:null, 
     withCredentials: true });
     return this.http.get(this.config.baseUrl + 
     this.config.getDropDownListForProject, requestOptions)
     .map(res => 
     {
      if(res != null)
      { 
        return res.json();
        //return true;
      }
    })
  .catch(this.handleError);
   }  

and add CORS in your backend PHP code where all api request will land first.

try this and let me know if it is working or not i had a same issue i was adding CORS from angular5 that was not working then i added CORS to backend and it worked for me