title: What is this 'isset($_POST)' code doing?
body: <p>Trying to understand what this isset($_POST) code is doing</p>
  
  <pre><code>if (isset($_POST['Submit'])) {
      $title=$_POST['title'];
      $forename = $_POST['forename']; 
      $surname=$_POST['surname'];
      $dob=$_POST['dob'];
      $gender=$_POST['gender'];
      $email=$_POST['email']; 
      $phone=$_POST['phone'];
      $password=$_POST['password'];
  
  
      if (authRegister($title, $forename, $surname, $dob, $gender, $email, $phone, $password))
      {
          echo 'Thank you for registering your details, you can now login';           
      } 
      else
      {
          outputErrors();
      }
  </code></pre>