title: Check for domain prefix in username login
body: <p>How do i check for <code>"AD\"</code> in a string? If someone tries to login using the domain prefix <code>"AD\"</code> - I want the application to ignore the <code>"AD\"</code> and check for username after the first 3 characters..</p>
  
  <p>I have tried:</p>
  
  <pre><code>if (strpos($username, "AD\\") !== false) {
      $username = substr($username, 3);
  }
  </code></pre>
  
  <p>but this does not work.</p>