Angular PHP Authorization Header API Call Fails

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I am working on a login page functionality in a SPA built with Angular CLI. My backend is tomcat, php with mysql on a hosting server to which I am able to successfully connect, get and update via post call all the other content in the app using httpclient module. I run CLI with proxy. App is running at localhost:4200

Without Authorization Header, API calls succeeds and I get the proper response:

{"status":true,"resp":"Login Success."} 

from my login.php file.

Login Service:

const headers = new HttpHeaders({
  'Content-Type': 'application/x-www-form-urlencoded',
  'Authorization': 'Basic ' + btoa(email+':'+pwd)    <---Including this line gives me error
});