SilverStripe PayPal Mini Cart Integration

(contentcontrollerInit) MiniCart.php

<?php

class MiniCart extends DataObjectDecorator {

	...

	function contentcontrollerInit($controller) {
		Requirements::javascript(
			MODULE_MINICART_DIR . '/thirdparty/minicart/minicart.js'
		);
		Requirements::customScript('PAYPAL.apps.MiniCart.render();', 'minicart');
	}

}

(MiniCartItemShortcodeHandler) MiniCart.php

<?php

class MiniCart extends DataObjectDecorator {

	...

	public static function MiniCartItemShortcodeHandler($attributes, $content = null, $parser = null) {

		if(empty($attributes['name']) || empty($attributes['price'])) {
			return;
		}
		$item_name = $attributes['name'];
		$item_price = $attributes['price'];
		$button = (!empty($content)) ? $content : "Add to cart";

		$data = new ArrayData(
			array(
				'ItemName' => $item_name,
				'Amount' => $item_price,
				'Button' => $button,
				'Business' => self::$business_email,
				'CurrencyCode' => self::$currency_code,
				'Return' => self::$return_url,
				'Cancel' => self::$cancel_return_url
			)
		);

		return $data->renderWith('MiniCartItem');
	}

	...

}

(Start) MiniCart.php

<?php

class MiniCart extends DataObjectDecorator {

	protected static $business_email = "labs-feedback-minicart@paypal.com";
	protected static $currency_code = "USD";
	protected static $return_url = "https://minicart.paypal-labs.com/?success";
	protected static $cancel_return_url = "https://minicart.paypal-labs.com/?cancel";

	public static function set_business_email($email) {
		self::$business_email = $email;
	}
	public static function set_currency_code($code) {
		self::$currency_code = $code;
	}
	public static function set_return_url($url) {
		self::$return_url = $url;
	}
	public static function set_cancel_return_url($url) {
		self::$cancel_return_url = $url;
	}

}

(ViewCart) MiniCart.php

<?php

class MiniCart extends DataObjectDecorator {

	...

	public function ViewCart($button = "View your cart") {

		$data = new ArrayData(
			array(
				'Business' => self::$business_email,
				'Button' => $button
			)
		);

		return $data->renderWith('ViewCart');
	}

	...

}

_config.php

<?php

define('MODULE_MINICART_DIR', 'module_minicart');

DataObject::add_extension('SiteTree', 'MiniCart');

ShortcodeParser::get()->register('mini_cart_item', array('MiniCart', 'MiniCartItemShortcodeHandler'));

MiniCart::set_business_email("me@example.com");
MiniCart::set_currency_code("USD");
MiniCart::set_return_url("https://example.com/page?success");
MiniCart::set_cancel_return_url("https://example.com/page?cancel");

MiniCartItem.ss

<form action="https://www.paypal.com/cgi-bin/webscr" method="post">
	<fieldset>
		<input type="hidden" name="cmd" value="_cart" />
		<input type="hidden" name="add" value="1" />
		<input type="hidden" name="business" value="$Business" />
		<input type="hidden" name="item_name" value="$ItemName" />
		<input type="hidden" name="amount" value="$Amount" />
		<input type="hidden" name="currency_code" value="$CurrencyCode" />
		<input type="hidden" name="return" value="$Return" />
		<input type="hidden" name="cancel_return" value="$Cancel" />
		<p><strong>$ItemName</strong><br />${$Amount}</p>
		<input type="submit" name="submit" value="$Button" class="button" />
	</fieldset>
</form>

ViewCart.ss

<form action="https://www.paypal.com/cgi-bin/webscr" method="post" class="last"> 
	<fieldset>
		<input type="hidden" name="business" value="$Business" /> 
		<input type="hidden" name="cmd" value="_cart" /> 
		<input type="hidden" name="display" value="1" /> 
		<input type="submit" name="submit" value="$Button" class="button" />
	</fieldset>
</form>