Question

The $base variable in the code below is apparently outside the scope, however the $urlS and $urlE variables are not? Can someone explain why this is?

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&f=l1';
private $rate;

public function __construct($toCurr) {
$url = self::$urlS.$base.$toCurr.self::$urlE;

Answer 1

You need to include self:: before $base, as you did with $urlS and $urlE:

$url = self::$urlS . self::$base . $toCurr . self::$urlE;