title: Codeigniter encryption class producing inconsistent results
body: <p>I am testing out the codeigniter encrypt library and can not seem to get consistent results. 
  I set up a test page which basically just has the following code</p>
  
  <pre><code>    $pwd = "test string";
      $key = "testkey_obviously_it_will_be_more_secure";
      for ($i=0; $i&lt;11; $i++){
          echo $this-&gt;encrypt-&gt;encode($pwd, $key)."&lt;br&gt;";
      }
  </code></pre>
  
  <p>The output is 10 completely different lines of characters.</p>
  
  <p>I am obviously doing something wrong but I can't see what it could be. I have tried using the encode function with and without a $key but the results are the same for me.</p>
  
  <p>By the way, I am using codeigniter 2.1.0 in my test environment</p>