title: Get file value before upload
body: <p>How can i get file value before upload? This is example code.</p>
  
  <pre><code>&lt;html&gt;
  &lt;head&gt;
  &lt;title&gt;Upload Form&lt;/title&gt;
  &lt;/head&gt;
  &lt;body&gt;
  &lt;?php echo $error;?&gt; &lt;!-- Error Message will show up here --&gt;
  &lt;?php echo form_open_multipart('upload_controller/do_upload');?&gt;
  &lt;?php echo "&lt;input type='file' name='userfile' size='20' /&gt;"; ?&gt;
  &lt;?php echo "&lt;input type='submit' name='submit' value='upload' /&gt; ";?&gt;
  &lt;?php echo "&lt;/form&gt;"?&gt;
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>This is controller.</p>
  
  <pre><code>           ...
  
         public function do_upload()
         {
            ///////////////////////////////////////////////
            // Hear i want to show filename before upload.
            ///////////////////////////////////////////////
            echo var_dump( $this-&gt;input-&gt;post('userfile') );
            ///////////////////////////////////////////////
  
            ...
         }
  </code></pre>
  
  <p>I try to show "userfile" value, But it alway show null. How can i show this value.</p>