/**

* A array of name value pairs representing the seller's API Username, Password & Signature.

*

* These are passed to the class via the parameters in the constructor.

*/

private $api_credentials;

/**

* The PayPal API URL Defaults to https://api-3t.sandbox.paypal.com/nvp when in

* sandbox mode and https://api-3t.paypal.com/nvp when live.

*/

private $endpoint;

/**

* The PayPal URL for initialing the popup payment process.

*

* Defaults to https://www.sandbox.paypal.com/incontext?token=**** for sandbox mode

* and https://www.paypal.com/incontext?token=**** in live mode.

*/

private $checkout_url;

/**

* Stores the token once it has been acquired from PayPal

*/

protected $token;

/**

* The URL on your site that the purchaser is sent to upon completing checkout.

*/

public $return_url;

/**

* The URL on your site that the purchaser is sent to when cancelling a payment during the checkout process.

*/

public $cancel_url;

/**

* Creates a PayPal Digital Goods Object configured according to the parameters in the args associative array.

*

* Available $args parameters:

* - cancel_url, string, required. The URL on your site that the purchaser is sent to when cancelling a payment during the checkout process.

* - return_url, string, required. The URL on your site that the purchaser is sent to upon completing checkout.

* - notify_url, string, optional. The URL for receiving Instant Payment Notification (IPN) about this transaction.

* - solution_type, string, optional. Type of checkout flow. It is one of Sole (default, buyer does not need to create a PayPal account to check out) or Mark (buyer must have a PayPal account to check out)

* - sandbox, boolean. Flag to indicate whether to use the PayPal Sandbox or live PayPal site. Default true - use sandbox.

* - business_name, string. A label that overrides the business name in the PayPal account on the PayPal hosted checkout pages.

*

* @param api_credentials, required, a name => value array containing your API username, password and signature.

* @param args, named parameters to customise the subscription and checkout process. See description for available parameters.

*/

public function __construct( $args = array() ){

if( '' == PayPal_Digital_Goods_Configuration::username() || '' == PayPal_Digital_Goods_Configuration::password() || '' == PayPal_Digital_Goods_Configuration::signature() )

throw new Exception( 'You must specify your PayPal API username, password & signature in the $api_credentials array.' );

elseif( ( empty( $args['return_url'] ) && '' == PayPal_Digital_Goods_Configuration::username() ) || ( empty( $args['cancel_url'] ) && '' == PayPal_Digital_Goods_Configuration::cancel_url() ) )

throw new Exception( 'You must specify a return_url & cancel_url.' );

$defaults = array(

'sandbox' => true,

'business_name' => '',

'solution_type' => 'Sole',

'return_url' => PayPal_Digital_Goods_Configuration::return_url(),

'cancel_url' => PayPal_Digital_Goods_Configuration::cancel_url(),

'notify_url' => PayPal_Digital_Goods_Configuration::notify_url(),

'display_address' => PayPal_Digital_Goods_Configuration::display_address(),

'locale_code' => PayPal_Digital_Goods_Configuration::locale_code(), // Defaults to 'US'

);

$args = array_merge( $defaults, $args );

$this->currency = PayPal_Digital_Goods_Configuration::currency();

$this->business_name = $args['business_name'];

$this->return_url = $args['return_url'];

$this->cancel_url = $args['cancel_url'];

$this->notify_url = $args['notify_url'];

$this->solution_type = $args['solution_type'];

$this->display_address = $args['display_address'];

$this->locale_code = $args['locale_code'];

}

/**

* Map this object's API credentials to the PayPal NVP format for posting to the API.

*

* Abstracted from @see get_payment_details_url for readability.

*/

protected function get_api_credentials_url(){

return 'USER=' . urlencode( PayPal_Digital_Goods_Configuration::username() )

. '&PWD=' . urlencode( PayPal_Digital_Goods_Configuration::password() )

. '&SIGNATURE=' . urlencode( PayPal_Digital_Goods_Configuration::signature() )

. '&VERSION='. urlencode( PayPal_Digital_Goods_Configuration::version() );

}

/**

* Map this object's transaction details to the PayPal NVP format for posting to PayPal.

*

* @param $action, string. The PayPal NVP API action to create the URL for. One of SetExpressCheckout, CreateRecurringPaymentsProfile or GetRecurringPaymentsProfileDetails.

* @param $profile_id, (optional) string. A PayPal Recurrent Payment Profile ID, required for GetRecurringPaymentsProfileDetails operation.

* @return string A URL which can be called with the @see call_paypal() method to perform the appropriate API operation.

*/

protected function get_payment_details_url( $action, $profile_or_transaction_id = '' ){

if( empty( $this->token ) && isset( $_GET['token'] ) )

$this->token = $_GET['token'];

// Setup the Payment Details

$api_request = $this->get_api_credentials_url();

// Parameters to Request Recurring Payment Token

if( 'SetExpressCheckout' == $action ) {

$api_request .= '&METHOD=SetExpressCheckout'

. '&RETURNURL=' . urlencode( $this->return_url )

. '&SOLUTIONTYPE=' . urlencode( $this->solution_type )

. '&LOCALECODE=' . urlencode( $this->locale_code )

. '&CANCELURL=' . urlencode( $this->cancel_url )

. '&NOSHIPPING=' . ( $this->display_address == 'yes' ? 2 : 1 );

if( ! empty( $this->business_name ) )

$api_request .= '&BRANDNAME=' . urlencode( $this->business_name );

} elseif ( 'GetExpressCheckoutDetails' == $action ) {

$api_request .= '&METHOD=GetExpressCheckoutDetails'

. '&TOKEN=' . $this->token;

}

return $api_request;

}

/**

* Creates a payment profile with PayPal represented by the token it returns.

*

* When a buyer clicks the Pay with PayPal button, this function calls the PayPal SetExpressCheckout API operation.

*

* It passes payment details of the items purchased and therefore, set_payment_details() must have been called

* before this function.

*

* Return:

*

*/

public function request_checkout_token(){

$response = $this->call_paypal( 'SetExpressCheckout' );

$this->token = $response['TOKEN'];

return $response;

}

/**

* Calls the PayPal GetExpressCheckoutDetails methods and returns a more nicely formatted response

*

* Called internally on return from set_express_checkout(). Can be called anytime to get details of

* a transaction for which you have the Token.

*/

public function get_checkout_details(){

return $this->call_paypal( 'GetExpressCheckoutDetails' );

}

/**

* Post to PayPal

*

* Makes an API call using an NVP String and an Endpoint. Based on code available here: https://www.x.com/blogs/Nate/2011/01/07/digital-goods-with-express-checkout-in-php

*

* @param action, string, required. The API operation to be performed, eg. GetExpressCheckoutDetails. The action is abstracted from you (the developer) by the appropriate helper function eg. GetExpressCheckoutDetails via get_checkout_details()

*/

protected function call_paypal( $action, $profile_id = '', $status = '', $args = array() ){

// Use the one function for all PayPal API operations

$api_parameters = $this->get_payment_details_url( $action, $profile_id, $status, $args );

$ch = curl_init();

curl_setopt( $ch, CURLOPT_URL, PayPal_Digital_Goods_Configuration::endpoint() );

curl_setopt( $ch, CURLOPT_VERBOSE, 1 );

// Make sure we use TLS as PayPal no longer supports SSLv3: https://ppmts.custhelp.com/app/answers/detail/a_id/1191/session/L2F2LzEvdGltZS8xNDE2MzUyMTgwL3NpZC8tVzFLaU03bQ%3D%3D

curl_setopt( $ch, CURLOPT_SSLVERSION, 1 );

// Turn off server and peer verification

curl_setopt( $ch, CURLOPT_SSL_VERIFYPEER, FALSE );

curl_setopt( $ch, CURLOPT_SSL_VERIFYHOST, FALSE );

curl_setopt( $ch, CURLOPT_RETURNTRANSFER, 1 );

curl_setopt( $ch, CURLOPT_POST, 1 );

// Set the API parameters for this transaction

curl_setopt( $ch, CURLOPT_POSTFIELDS, $api_parameters );

// Request response from PayPal

$response = curl_exec( $ch );

// If no response was received from PayPal there is no point parsing the response

if ( ! $response ) {

throw new Exception( $action . ' failed: ' . curl_error( $ch ) . '(' . curl_errno( $ch ) . ')' );

}

curl_close( $ch );

// An associative array is more usable than a parameter string

parse_str( $response, $parsed_response );

if ( ( 0 == sizeof( $parsed_response ) ) || ! array_key_exists( 'ACK', $parsed_response ) ) {

throw new Exception( "Invalid HTTP Response for POST request($api_parameters) to " . PayPal_Digital_Goods_Configuration::endpoint() );

}

if ( $parsed_response['ACK'] == 'Failure' ) {

throw new Exception( "Calling PayPal with action $action has Failed: " . $parsed_response['L_LONGMESSAGE0'], $parsed_response['L_ERRORCODE0'] );

}

return $parsed_response;

}

/**

* Returns this instance of the class's token.

*/

public function token(){

if ( empty( $this->token ) ) {

$this->request_checkout_token();

}

return $this->token;

}

/**

* The Javascript to invoke the digital goods in context checkout process.

*

* No need to call this function manually, required scripts are automatically printed with @see print_buy_buttion().

* If you do print this script manually, print it after the button in the DOM to ensure the

* click event is properly hooked.

*/

public function get_script( $args = array() ){

if( empty( $args['element_id'] ) )

$args['element_id'] = 'paypal-submit';

$dg_script = '<script src ="https://www.paypalobjects.com/js/external/dg.js" type="text/javascript"></script>'

. '<script>'

. 'var dg = new PAYPAL.apps.DGFlow({'

. 'trigger: "' . $args['element_id'] . '"' // the ID of the HTML element which calls setExpressCheckout

. '}); </script>';

return $dg_script;

}

/**

* Create and return the Buy (or Subscribe) button for your page.

*

* The button can be output either as a link to a image submit button, link to a page

* or link directly to PayPal (default).

*

* The simplest method is to pass no parameters and have the button be a link directly to

* PayPal; however, the drawback of this approach is a slower load time for the page on which

* the button is included.

*

* @param args array. Name => value parameters to customise the buy button.

* 'id' string. The id of the submit element. Defaults to 'paypal-submit'.

* 'element' string. The type of element to use as the button. Either anchor or submit. Default 'anchor'.

* 'href' string. The URL for 'anchor' tag. Ignored when 'element' is 'submit'. Default $this->checkout_url.

* 'get_token' boolean. Whether to include a token with the href. Overridden by 'element' when it is 'submit'.

* 'type' string. Type of element to output, either anchor or image/submit. Defaults to 'anchor'.

*/

public function get_buy_button( $args = array() ){

$defaults = array(

'id' => 'paypal-submit',

'type' => 'anchor',

'href' => PayPal_Digital_Goods_Configuration::checkout_url(),

'alt' => 'Submit',

'get_token' => true,

'locale' => 'en_US'

);

$args = array_merge( $defaults, $args );

if( $args['type'] == 'anchor' ) {

if( $args['get_token'] == true && empty( $this->token ) )

$this->request_checkout_token();

// Include the token in the href if the default href is not overridden

if( $args['href'] == PayPal_Digital_Goods_Configuration::checkout_url() )

$args['href'] .= $this->token;

$button = '<a href="' . $args['href'] . '" id="' . $args['id'] . '" alt="' . $args['alt'] . '"><img src="https://www.paypal.com/' . $args['locale'] . '/i/btn/btn_dg_pay_w_paypal.gif" border="0" /></a>';

} else {

$button = '<input type="image" id="' . $args['id'] . '" alt="' . $args['alt'] . '" src="https://www.paypal.com/' . $args['locale'] . '/i/btn/btn_dg_pay_w_paypal.gif">';

}

return $button;

}

/**

* Print the Buy (or Subscribe) button for this API object as well as the scripts

* required by the button.

*

* If you want to manually insert the script at a different position in your page,

* you can manually call @see get_buy_button() & @see get_script().

*

* @uses get_buy_button()

* @uses get_script()

*/

public function print_buy_button( $args = array() ){

echo $this->get_buy_button( $args );

echo $this->get_script( $args );

}

/**

* Returns the Checkout URL including a token for this transaction.

*/

public function get_checkout_url() {

if ( empty( $this->token ) ) {

$this->request_checkout_token();

}

// Include the token in the href if the default href is not overridden

return PayPal_Digital_Goods_Configuration::checkout_url() . $this->token;

}

/**

* Get the symbol associated with a currency, optionally specified with '$currency_code' parameter.

*

* Will always return the symbol and can optionally also print the symbol.

*

* @param $currency_code, string, optional, the ISO 4217 Code of the currency for which you want the Symbol, default the currency code of this object

* @param $echo bool, Optionally print the symbol before returning it.

**/

public function get_currency_symbol( $currency_code = '', $echo = false ){

if ( empty( $currency_code ) ) {

$currency_code = PayPal_Digital_Goods_Configuration::currency();

}

switch( $currency_code ) {

case 'AUD' :

case 'CAD' :

case 'NZD' :

case 'SGD' :

case 'HKD' :

case 'TWD' :

case 'USD' :

$currency_symbol = '$';

break;

case 'DKK' :

case 'NOK' :

case 'SEK' :

$currency_symbol = 'kr';

break;

case 'EUR' :

$currency_symbol = '&euro;';

break;

case 'GBP' :

$currency_symbol = '&pound;';

break;

case 'JPY' :

$currency_symbol = '&yen;';

break;

case 'CZK' :

$currency_symbol = 'Kč';

break;

case 'HUF' :

$currency_symbol = 'Ft';

break;

case 'PLN' :

$currency_symbol = 'zł';

break;

case 'CHF' :

$currency_symbol = 'CHF';

break;

}

if( $echo )

echo $currency_symbol;

return $currency_symbol;

}

/**

* Get the description of this payment

*/

abstract public function get_description();

/**

* A unified API for processing a payment or subscription.

*/

abstract public function process();

/**

* A unified API for getting the details of a purchase or subscription.

*/

abstract public function get_details( $transaction_or_profile_id );