title: CodeIgniter Setting config item that is in array
body: <p>So I just started using CodeIgniter... and got stuck in setting config item</p>
  
  <p>I have read that replacing the value of a config item is as easy as this:</p>
  
  <pre><code>$this-&gt;config-&gt;set_item('item_name', 'item_value');
  </code></pre>
  
  <p>But what if I want to set a config item that is part of an array of config items... like this one:</p>
  
  <pre><code>$api_config = $this-&gt;config-&gt;load('api'); //loading the created configuration under config folder
  </code></pre>
  
  <p>api.php</p>
  
  <pre><code>$facebook['app_id'] = '123213213';
  $facebook['api_key'] = '123123WERWERWE123123';
  
  $config['facebook'] = $facebook;
  </code></pre>
  
  <p>and I want to dynamically replace app_id.</p>