Model/ArticleToExpressCheckoutValidator.php
public function isArticleValid()
    {
        $valid = true;
        if ($this->isArticleAmountZero() || $this->isSameItemInBasket()) {
            $valid = false;
        }

        return $valid;
    }
public function isArticleValid()
    {
        $valid = true;
        if ($this->isArticleAmountZero() || $this->isSameItemInBasket()) {
            $valid = false;
        }

        return $valid;
    }
public function isArticleValid ( ) { $ valid = true ; if ( $ this -> isArticleAmountZero ( ) || $ this -> isSameItemInBasket ( ) ) { $ valid = false ; } return $ valid ; }
Method returns if article valid

@return bool
Method returns if article valid