title: CakePHP 3.6 File Upload Returns Missing field '...' in POST data
body: <p>I am attempting to add a file/image upload form to my site, and I am getting the following error</p>
  
  <pre><code>Unexpected field 'uploadfile' in POST data, Missing field 'uploadfile.name, uploadfile.type, uploadfile.tmp_name, uploadfile.error, uploadfile.size' in POST data
  </code></pre>
  
  <p>from the following form code</p>
  
  <pre><code>&lt;?= $this-&gt;Form-&gt;create(null, ['id' =&gt; 'save_upload_image', 'url' =&gt; "/research_station/save_upload_image", 'class' =&gt; 'upload-file']) ?&gt;
  
      &lt;div class="form-group"&gt;
          &lt;?= $this-&gt;Form-&gt;control('uploadname', ['id' =&gt; 'uploadname']) ?&gt;
      &lt;/div&gt;
  
      &lt;div class="form-group"&gt;
          &lt;?= $this-&gt;Form-&gt;file('uploadfile', array('name' =&gt; 'uploadfile', 'type' =&gt; 'file')) ?&gt;
      &lt;/div&gt;
  
      &lt;?= $this-&gt;Form-&gt;button('Upload', ['class' =&gt; 'btn btn-success btn-pill pull-right']) ?&gt;
  
  &lt;?= $this-&gt;Form-&gt;end() ?&gt;
  </code></pre>
  
  <p>Any ideas on what I am doing wrong?</p>