Bind Validation to “Process to checkout” button in Magento

Bind Validation to “Process to checkout” button in Magento.md

As per request by a customer, they need to add a customised validation in the checkout process. The customer cannot proceed to checkout in some circumstances:

The grand total of the shopping cart exceed a certain amount There is at least one product in the shopping cart belongs to a certain category If all of the conditions above is met, then the customer cannot checkout. In this case, I just disabled the “process to checkout” button.

The file been overloaded is

app\design\frontend\base\default\template\checkout\onepage\link.phtml

Original magento code is

<?php if ($this->isPossibleOnepageCheckout()):?>
<button type=”button” title=”<?php echo $this->__(‘Proceed to Checkout’) ?>” class=”button btn-proceed-checkout btn-checkout<?php if ($this->isDisabled()):?> no-checkout<?php endif; ?>”<?php if ($this->isDisabled()):?> disabled=”disabled”<?php endif; ?> onclick=”window.location='<?php echo $this->getCheckoutUrl() ?>’;”><span><span><?php echo $this->__(‘Proceed to Checkout’) ?></span></span></button>
<?php endif?>

I put some overhead to grab the grand total and the category (categories) for each product in the shopping cart. Later on, I put my flag in as part of the magento’s if statement.

<?php if ($this->isPossibleOnepageCheckout()):?>
	<?php
		$grandTotalLimit = floatval(200);
		$freeGiftCategoryId = 4;
		$canCheckout = true;
		
		$cart = Mage::getModel('checkout/cart')->getQuote();
		$grandTotal = $this->helper('checkout/cart')->getQuote()->getGrandTotal();
// 		echo 'grandtotal = ' . $grandTotal;
		foreach ($cart->getAllItems() as $item) 
		{
			$productName = $item->getProduct()->getName();
			$productPrice = $item->getProduct()->getPrice();
			$productCategoryIds = $item->getProduct()->getCategoryIds();
			foreach ($productCategoryIds as $productCategoryId)
			{
				if($canCheckout === true && (doubleval($grandTotal) < doubleval($grandTotalLimit)) && (intval($productCategoryId) === intval($freeGiftCategoryId)))
					$canCheckout = false;
			}
		}
	?>
    <button type="button" title="<?php echo $this->__('Proceed to Checkout') ?>" class="button btn-proceed-checkout btn-checkout<?php if ($this->isDisabled()):?> no-checkout<?php endif; ?>"<?php if ($this->isDisabled() || $canCheckout !== true):?> disabled="disabled"<?php endif; ?> onclick="window.location='<?php echo $this->getCheckoutUrl() ?>';"><span><span><?php echo $this->__('Proceed to Checkout') ?></span></span></button>
<?php endif?>

The result is successful. This could be a bad practice when modifying magento, as well as the customer does not get any reasoning hence may be confused by the disabled “process to checkout” button.