title: Multiple select validation not working in Codeigniter
body: <p>I have a multiple select box and I am using CI to validate drop down with custom CI validation library. But it's always produce string while its produce an array of selected items. </p>
  
  <pre><code>&lt;select multiple="" class="form-control" name="course[]" id="course"&gt;
      &lt;option value=""&gt;Select Course&lt;/option&gt;
      &lt;option value="38833851"&gt;B.com&lt;/option&gt; 
      &lt;option value="31068174"&gt;B.Sc Nursing&lt;/option&gt;
      &lt;option selected="selected" value="7771143"&gt;B.Tech&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>and in controller</p>
  
  <pre><code> $this-&gt;form_validation-&gt;set_rules('course[]', 'course name','required|multiple_select');
  </code></pre>
  
  <p>and other thing. I have created a another custom validation library.</p>
  
  <pre><code>class MY_Form_validation extends CI_Form_validation{
      protected $CI;
      public function __construct(){
          parent::__construct();
          $this-&gt;CI =&amp; get_instance();
      }
  
      public function multiple_select($array){
          print_r($array); die;
          $this-&gt;CI-&gt;form_validation-&gt;set_message('multiple_select', 'Select at least one %s');
          if(empty($array)){
              return false;
          }else{
              return true;
          }
      }
  }
  </code></pre>
  
  <p>But <code>$array</code> always print a string.</p>
  
  <p>Please provide any solution.</p>