e credit card number.
        @return Returns name of the provider; values can be &lt;code>"visa"&lt;/code>, &lt;code>"mastercard"&lt;/code>, &lt;code>"discover"&lt;/code>, &lt;code>"amex"&lt;/code>, &lt;code>"diners"&lt;/code>, &lt;code>"other"&lt;/code> or &lt;code>"invalid"&lt;/code>.
    */
    public static function getCreditCardProvider(cardNumber:String):String {
        if (!ValidationUtil.isCreditCard(cardNumber))
            return 'invalid';
        
        if (cardNumber.length == 13 ||
       