title: two dimension session issue with codeigniter
body: <p>I want to store two dimensional array in session, where i keep creating the array through a function call.</p>
  
  <p>I am trying with this code</p>
  
  <pre><code>function nextQuestion($questionId,$response)
  { 
         $this-&gt;session-&gt;set_userdata("res[$questionId][]"),$response);
  }
  </code></pre>
  
  <p>but this is not creating a two dimensional array</p>