title: array_shift shows warning if the variable has a null or empty value
body: <p>I'm working on a MVC project and i'm on the part to get the URL values, to get each param i use <a href="http://php.net/manual/en/function.array-shift.php" rel="nofollow">array_shift()</a> and the documentation says this: </p>
  
  <blockquote>
    <p>Returns the shifted value, or <strong>NULL</strong> if array is empty or is not an
    array.</p>
  </blockquote>
  
  <p>In my code i have these lines:</p>
  
  <pre><code>        $arrParams = isset($_GET["params"]) ? explode("/", $_GET["params"]) : "";
  
          $controller = array_shift($arrParams);
          $action = array_shift($arrParams);
          $params = array_shift($arrParams);
  </code></pre>
  
  <p>If i access to <code>mvc-project.local</code> and i don't pass any param to the URL appears this message: </p>
  
  <blockquote>
    <p>Warning: array_shift() expects parameter 1 to be array, string given in ... on line 12</p>
  </blockquote>
  
  <p>Where is the problem?</p>