Redo2

<?php

class PromotionCode
{
    private $promoCode;
    private $idAccount;

    const INVALID_CODE = 'The code you entered is invalid.';

    /**
     * Construct object with idAccount and user entered promotional code.
     *
     * @idAccount (int)
     * @promoCode (string)
    */
    public function __construct($idAccount, $promoCode)
    {
        $this->promoCode = $promoCode;
        $this->idAccount = $idAccount;

        // Do some simple validation prior to running queries.
        if(!$this->simpleValidation()) {
            throw new Exception($this::INVALID_CODE);
        }
    }

    /**
     * Process redemption of promotional code under account.
    */
    public function redeem()
    {
        // ...
    }

    protected function simpleValidation()
    {
        // Fail if code is not 12 characters.
        if(strlen($this->promoCode) <> 12) return false;

        // Fail is code doesn't begin with a letter.
        if(ctype_digit(substr($this->promoCode, 0, 1))) return false;

        return true;
    }
}

try {
    $redeem = new PromotionCode(30, "MN45QZ8HT9PN");
    $redeem->redeem();
} catch(Exception $e) {
    echo $e->getMessage();
}

?>