title: PhpStorm code completion doesn't show core classes/extensions
body: <p>I'm having trouble with PHPStorm. I just started new project created a couple of my own classes, in one of them I created PDO object.</p>
  
  <pre><code>$this-&gt;cnn = new PDO("sqlite:db/base.db");
  </code></pre>
  
  <p>Now when I want to see what kind of methods this object has via crtl + whitespace, I get no suggestions. Then I tried to see the list of classes available to me with.</p>
  
  <pre><code>$newClass = new
  </code></pre>
  
  <p>And when I pressed ctrl + whitespace it only showed me the classes I created.</p>
  
  <p>So the question is, what do i need to do, to make PhpStorm see all the classes that are available (not just the ones i created).</p>
  
  <p>P.S. when i ctrl + click on PDO (which is underlined) it says that class is undefined</p>
  
  <p>P.P.S. in project settings i have selected php 5.4 language language and selected interpreter (php 5.4.7, using xampp)</p>