title: All Drupal function undefined in module page
body: <p>I had created my own module in D7. I created a new php page, callback.php, and access in my browser with url: ww.xxx.com/sites/all/modules/custom/seaqueen_module/pages/callback.php</p>
  
  <p>When it calls any drupal function, such as drupal_set_message(), it shows error:<br/>
  Fatal error: Call to undefined function drupal_set_message()</p>
  
  <p>The same happens to other function such as  db_select(), db_insert(), db_update() , etc.</p>
  
  <p>This error only occurs in the page callback.php, while other pages in this module works perfectly.</p>
  
  <p>In my module .info file, I had inserted row below:</p>
  
  <pre><code>files[] = pages/callback.php 
  </code></pre>
  
  <p>Cache is cleared and same error occurs. Is there anything I missed out and cause this error?</p>