/**
 * NOTICE: This class begins in Part 1 of this tutorial! It is the same class, Paypal_Client, but with additional code.
 * New class variable needed by the ecSetExpressCheckout API call.
 *
 * The live URL is: https://www.paypal.com/webscr
 * The test URL is: https://www.sandbox.paypal.com/webscr
 *
 * Let's use the test URL for now
 *
 * @var string The express checkout page URL
 */
public $api_expresscheckout_uri = 'https://www.sandbox.paypal.com/webscr';

/**
*
* Calls the 'ECDoExpressCheckout' API call. Requires a token that can
* be obtained using the 'SetExpressCheckout' API call. The payer_id is
* obtained from the 'SetExpressCheckout' or 'GetExpressCheckoutDetails' API call.
*
* @param string $token
* @param string $payer_id
* @param float  $payment_amount
* @param string $currency_code
* @param string $payment_action Can be 'Authorization', 'Sale', or 'Order'
*
* @return Zend_Http_Response
* @throws Zend_Http_Client_Exception
*/
function ecDoExpressCheckout($token, $payer_id, $payment_amount, $currency_code, $payment_action = 'Sale') {
	$this->setParameterGet('METHOD', 'DoExpressCheckoutPayment');
	$this->setParameterGet('AMT', $payment_amount);
	$this->setParameterGet('TOKEN', $token);
	$this->setParameterGet('PAYERID', $payer_id);
	$this->setParameterGet('PAYMENTACTION', $payment_action); // Can be 'Authorization', 'Sale', or 'Order'
 
	return $this->request(Zend_Http_Client::GET);
}
 
/**
* Request an authorization token.
*
* @param float $paymentAmount
* @param string $returnURL
* @param string $cancelURL
* @param string $currencyID
* @param string $payment_action Can be 'Authorization', 'Sale', or 'Order'. Default is 'Authorization'
* @return Zend_Http_Response
*/
function ecSetExpressCheckout($paymentAmount, $returnURL, $cancelURL, $currencyID, $payment_action = 'Authorization') {
	$this->setParameterGet('METHOD', 'SetExpressCheckout');
 
	// The paypal PDF says to use this and not AMT, but in practice, 
	// that doesnt work yet as of the time of this writting...
//	    $this->setParameterGet('PAYMENTREQUEST_0_AMT', $paymentAmount);
 
	// ...So we will do this for now.
	$this->setParameterGet('AMT', $paymentAmount);
 
	$this->setParameterGet('RETURNURL', $returnURL);
	$this->setParameterGet('CANCELURL', $cancelURL);
	$this->setParameterGet('PAYMENTREQUEST_0_PAYMENTACTION', $payment_action); // Can be 'Authorization', 'Sale', or 'Order'
 
	return $this->request(Zend_Http_Client::GET);
}

/**
* Parse a Name-Value Pair response into an object.
* @param string $response
* @return object Returns an object representation of the response.
*/
public static function parse($response) {
 
	$responseArray = explode("&", $response);
 
	$result = array();
 
	if (count($responseArray) > 0) {
		foreach ($responseArray as $i => $value) {
 
			$keyValuePair = explode("=", $value);
 
			if(sizeof($keyValuePair) > 1) {
				$result[$keyValuePair[0]] = urldecode($keyValuePair[1]);
			}
		}
	}
 
	if (empty($result)) {
		$result = null;
	} else {
		$result = (object) $result;
	}
 
	return $result;
}

<?php
/**
 * Checkout Page. This is our starting point before sending off 
 * a request for the authorization token needed to authorize and
 * capture funds for this order. 
 */
 
// Assume we are displaying US dollars.
setlocale(LC_MONETARY, 'en_US');
 
$items = array(
	1001 => array(
		'name' => 'Dog Bowl',
		'quantity' => 1,
		'cost_per_unit' => 5.00,
		'weight_per_unit' => 0.5
	),
	1013 => array(
		'name' => 'Chew Toy',
		'quantity' => 3,
		'cost_per_unit' => 0.99,
		'weight_per_unit' => 1
	),
	201 => array(
		'name' => 'Doggy Mints',
		'quantity' => 1,
		'cost_per_unit' => 4.99,
		'weight_per_unit' => 2
	)
);
 
// ...Did the user submit the form?
if (!empty($_REQUEST['submit']) {
	// Great! They've confirmed their order.
	// Let's try out our new checkout code.
 
	// First off, we need to obtain an
	// authorization token.
 
	$adapter = new PayPal_Adapter();
 
	$amount = 0.0;
 
	foreach($items as $item) {
		$amount += $item['quantity'] * $item['cost_per_unit'];
	}
 
	$returnURL = 'https://www.yoursite.com/payment-complete.php';
	$cancelURL = 'https://www.yoursite.com/payment-cancelled.php';
 
	$currency_code = 'USD'; // Assuming we're using the US Dollar.
 
	// Let's ask for a token.
	$reply = $adapter->ecSetExpressCheckout(
		$amount, 
		$returnURL, 
		$cancelURL, 
		$currency_code
	);
 
	// ...If we succeed, we must redirected to PayPal at this point.
	if ($reply->isSuccessfull()) {
		// Let's turn that message body into something we can use...
		$replyData = $adapter->parse($reply->getBody());
 
		// If we did in fact succeed, we will now have a token to use
		if ($replyData->ACK == 'SUCCESS' || $replyData->ACK == 'SUCCESSWITHWARNING') {
 
			$token = $data->TOKEN; // ...It's already URL encoded for us.
 
			// Save the amount total... We must use this when we capture the funds.
			$_SESSION['CHECKOUT_AMOUNT'] = $amount;
 
			// Redirect to the PayPal express checkout page, using the token.
			header(
				'Location: ' . 
				$adapter->api_expresscheckout_uri . 
				'?&cmd=_express-checkout&token=' . $token
			);
		}
	} else {
		// Something went wrong.
		throw new Exception('ECSetExpressCheckout: We failed to get a successfull response from PayPal.');
	}
}
?>
 
<h1>Checkout</h1>
 
Here is your order. Please confirm your order by clicking the SUBMIT button.
 
<h2>Cart Items</h2>
<!-- This form will just submit to itself, and then our token request begins. -->
<form>
	<ul>
 
	<?php foreach($items as $sku => $item): ?>
		<?php 
		// Get each item's properties, and list them one item per row.
		$name = $item['name'];	
		$cpu = $item['cost_per_unit'];
		$quantity = $item['quantity'];
 
		$total_cost = $cpu * $quantity;
 
		?>
		<li>
			SKU <?php echo $sku; ?> - <?php echo $name; ?> (<?php echo money_format('%i', $total_cost); ?>)<br />
			<span style="font-size: xx-small"><?php echo $quantity; ?> @ <?php echo money_format('%i', $cpu); ?>each</span>
		</li>
	<?php endforeach; ?>
 
	</ul>
 
	<input type="submit" name="submit" value="SUBMIT" />
</form>

<?php
/**
 * payment-complete.php
 *
 * Payment complete page. As per our own request, this page is 
 * redirected to by PayPal when a payment is authorized (still need to capture the funds though). 
 */
 
// Instantiate our payment adapter
$adapter = new PayPal_Adapter();
 
// PayPal will call this page, and send back the 'confirm_payment' variable.
$paymentConfirmed = !empty($_REQUEST['confirm_payment']);
 
// ...Are we good to go?
if ($paymentConfirmed == true) {
	// Yes. We now have a token, and the payer ID needed
	// to call the ECDoExpressCheckout API call.
 
	$token = $_REQUEST['token'];
	$payer_id = $_REQUEST['PayerID'];
	$amount = $_SESSION['CHECKOUT_AMOUNT'];
	$currency_code = 'USD'; // Assuming we are still using the US Dollar.
 
	// Capture the funds!
	$reply = $adapter->ecDoExpressCheckout($token, $payer_id, $amount, $currency_code);
 
	// Did we get a valid reply?
	if ($reply->isSuccessfull()) {
		// Yes! We would usually save our order data at this point,
		// but, we can just output to the screen for now. :-)
		// The funds may or may not have been captured.
		// Check the $replyData->ACK property to know for sure.
 
		$replyData = $adapter->parse($reply->getBody());
 
		print_r($replyData);
 
		// Clean up.
		unset($_SESSION['CHECKOUT_AMOUNT']);
	} else {
		// No. Throw an exception.
		throw new Exception('We were unable to complete the ECDoExpressCheckout API call.');
	}
} else {
	// No. Throw an exception.
	throw new Exception('It appears we did not receive a confirmed payment flag.');
}
 
?>

<?php
/**
 * payment-cancelled.php
 *
 * Payment cancelled page. As per our own request, this page is 
 * redirected to by PayPal upon failed/cancelled payment. 
 */
?>
<h1>Payment Cancelled</h1>
<p>
	No charges were made.
</p>