title: dropzone.js sends empty $_FILES
body: <p>I try to use <a href="http://www.dropzonejs.com/" rel="nofollow">dropzone.js</a> to make a drag-and-drop file upload area and I'm getting really desperate here. I have this simplest script:</p>
  
  <pre><code>&lt;?php
    print_r($_FILES);
  ?&gt;
  
  &lt;!DOCTYPE html&gt;
  &lt;html lang="en"&gt;
      &lt;head&gt;
          &lt;meta http-equiv="content-type" content="text/html; charset=UTF-8"&gt; 
          &lt;meta charset="utf-8"&gt;
      &lt;/head&gt;
      &lt;body&gt;
          &lt;form action="/" method="POST" enctype="multipart/form-data" class="dropzone"&gt;
              &lt;input name="file" type="file" /&gt;
              &lt;input type="submit" name="submit" value="Submit" /&gt;
          &lt;/form&gt;
          &lt;script type='text/javascript' src="dropzone.js"&gt;&lt;/script&gt;
      &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>When I manually select the file using the file input button, I get this result:</p>
  
  <pre><code>Array ( [file] =&gt; Array ( [name] =&gt; test.txt [type] =&gt; text/plain [tmp_name] =&gt; C:\wamp\tmp\php4DFF.tmp [error] =&gt; 0 [size] =&gt; 247 ) )
  </code></pre>
  
  <p>However, when I use dropzone drag-and-drop, the file appears as uploaded, but after submitting I get this:</p>
  
  <pre><code>Array ( [file] =&gt; Array ( [name] =&gt; [type] =&gt; [tmp_name] =&gt; [error] =&gt; 4 [size] =&gt; 0 ) )
  </code></pre>
  
  <p>Also known as <strong>UPLOAD_ERR_NO_FILE</strong> <em>Value: 4; No file was uploaded.</em></p>
  
  <p>Am I missing something here?</p>
  
  <p>I tried to play with settings like <em>autoProcessQueue: false</em>, <em>autoDiscover: false</em>, automatic form submission, different scripts, different servers (apache/nginx), but absolutely nothing seems to work for me. There got to be some stupid thing that I'm just overseeing right now.</p>
  
  <p>I use dropzone.js v4.0.1 but I tried older versions as well.</p>