title: Md5 mix with upper and lowercase
body: <p>How can I generate md5 string with upper and lowercase letter?
  for example: TyUTExUM3Dw</p>
  
  <p>What I’ve tried</p>
  
  <pre><code>$id = $_GET['id'];
  
  $key = "SecreTkEy";
  $hash = md5($id.$key);
  
  echo $hash;
  </code></pre>