title: Codeigniter add new item to current session userdata array
body: <p>So I have this array:</p>
  
  <pre><code>$data = array(
    'item_1' =&gt; $this-&gt;input-&gt;post('item_1'),
    'item_2' =&gt; $this-&gt;input-&gt;post('item_2'),
    'item_3' =&gt; $this-&gt;input-&gt;post('item_3')
  );
  
  $this-&gt;session-&gt;set_userdata( 'items', $data );
  </code></pre>
  
  <p>And I want to add a new item to that array, so the updated array of userdata will be like this:</p>
  
  <pre><code>$data = array(
        'item_1' =&gt; $this-&gt;input-&gt;post('item_1'),
        'item_2' =&gt; $this-&gt;input-&gt;post('item_2'),
        'item_3' =&gt; $this-&gt;input-&gt;post('item_3'),
        'item_4' =&gt; $this-&gt;input-&gt;post('item_4')
  );
  
  $this-&gt;session-&gt;set_userdata( 'items', $data );
  </code></pre>
  
  <p>How to do that, Thank you</p>