title: Variable outside scope
body: <p>The <code>$base</code> variable in the code below is apparently outside the scope, however the <code>$urlS</code> and <code>$urlE</code> variables are not? Can someone explain why this is?</p>
  
  <pre><code>class Yahoo {
      //Code below to retrieve live currency rates from yahoo
  private static $base = 'USD';
  private static $urlS = LIVE_FEED_YAHOO;
  private static $urlE = '=X&amp;f=l1';
  private $rate;
  
  public function __construct($toCurr) {
  $url = self::$urlS.$base.$toCurr.self::$urlE;
  </code></pre>