This tutorial outlines the procedure for integrating PayPal Payment into PHP applications. PayPal, a widely-used online American payment system, facilitates easy transmission of funds via the internet. For a PHP application, integrating PayPal requires meticulous implementation of the PayPal API for payment processing, alongside developing a secure and reliable PHP script for file downloading to ensure a seamless user transaction experience.

PayPal offers diverse functionalities for monetary transactions online, enabling direct transfers to individuals and payments for various internet services. Recognized as a leading online payment gateway, PayPal is commonly implemented for processing transactions across web and mobile platforms. For merchants seeking to provide a range of payment solutions, Authorize.Net represents an alternative online payment gateway. Detailed instructions for integrating Authorize.Net using PHP are available in a dedicated tutorial. 

The integration of PayPal Payment Gateway into websites can be accomplished through several methods, including:

  • PayPal Payments Standard;
  • PayPal Checkout;
  • Subscriptions & Recurring Payments;
  • PayPal Invoicing;
  • PayPal Payouts.

The focus will be on PayPal Payments Standard due to its simplicity for integration with PHP. The tutorial will proceed with the integration of PayPal Payment Standards in PHP.

To streamline the process, repetition of class coding will be omitted. The necessary class will be included in the downloadable file, ensuring ease of access to the dbclass.php class without redundancy in coding.

Steps for Integrating PayPal Payment Gateway in PHP

  • Set up a database, define tables, and insert sample data;
  • Create a config.php file and adjust the necessary settings;
  • Make an index.php file to display products for purchase;
  • Construct a notify.php file to handle IPN and log payment details in the database;
  • Develop a cancel.php file for payment cancellation scenarios;
  • Form a return.php file to manage the post-payment process;
  • Design a style.css file to apply custom styles to the web elements.

1. Set up a database, define tables, and insert sample data

To generate a database, execute the subsequent query in MySQL.

CREATE DATABASE allphptricks;

To generate the tables, execute the following queries.

CREATE TABLE `products` (
  `id` int(10) NOT NULL AUTO_INCREMENT,
  `name` varchar(250) NOT NULL,
  `code` varchar(100) NOT NULL,
  `price` double(9,2) NOT NULL,
  `image` varchar(250) NOT NULL,
   PRIMARY KEY (`id`),
   UNIQUE KEY `code` (`code`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

The SQL file for this table with dummy data has already been attached. Simply download the complete zip file for this tutorial.

CREATE TABLE `payment_info` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `item_number` varchar(255) NOT NULL,
  `item_name` varchar(255) NOT NULL,
  `payment_status` varchar(255) NOT NULL,
  `amount` double(10,2) NOT NULL,
  `currency` varchar(255) NOT NULL,
  `txn_id` varchar(255) NOT NULL,
  `create_at` timestamp NOT NULL DEFAULT current_timestamp(),
   PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

Transfer sample data to the products table.

INSERT INTO `products` (`id`, `name`, `code`, `price`, `image`) VALUES
(1, 'Laptop Core i5', 'Laptop01', 100.00, 'product-images/laptop.jpg'),
(2, 'Laptop Bag', 'Bag01', 10.00, 'product-images/laptop-bag.jpg'),
(3, 'iPhone X', 'iphone01', 50.00, 'product-images/iphone.jpg');

2. Create a config.php file and adjust the necessary settings

Generate a config.php file, paste the provided code, and make essential modifications such as updating database credentials, database name, username, password, as well as adjusting your PayPal business email, return, cancel, and notify URLs, among other details.

<?php
// Database Configuration 
define('DB_HOST', 'localhost'); 
define('DB_NAME', 'Your Database Name'); 
define('DB_USERNAME', 'Your Database Username'); 
define('DB_PASSWORD', 'Your Database Password'); 

// PayPal Configuration
define('PAYPAL_EMAIL', 'Your PayPal Business Email'); 
define('RETURN_URL', 'https://www.your-website.com/return.php'); 
define('CANCEL_URL', 'https://www.your-website.com/cancel.php'); 
define('NOTIFY_URL', 'https://www.your-website.com/notify.php'); 
define('CURRENCY', 'USD'); 
define('SANDBOX', TRUE); // TRUE or FALSE 
define('LOCAL_CERTIFICATE', FALSE); // TRUE or FALSE

if (SANDBOX === TRUE){
	$paypal_url = "https://www.sandbox.paypal.com/cgi-bin/webscr";
}else{
	$paypal_url = "https://www.paypal.com/cgi-bin/webscr";
}
// PayPal IPN Data Validate URL
define('PAYPAL_URL', $paypal_url);

3. Make an index.php file to display products for purchase

Generate an index.php file and paste the provided code into it. This page will showcase all the products from the ‘products’ table, allowing users to conveniently purchase any item.

<?php
require_once('dbclass.php');
$db = new DB;
$db->query("SELECT * FROM `products`");
$products = $db->resultSet();
$db->close();
?>
<html>
<head>
<title>PayPal Payment Integration in PHP</title>
<link rel='stylesheet' href='css/style.css' type='text/css' media='all' />
</head>
<body>

<div style="width:700px; margin:50 auto;">
<h2>PayPal Payment Integration in PHP</h2>

<?php
if( !empty($products) )
{
    foreach($products as $product)
    {
?>
        <div class='product_wrapper'>
        <div class='image'><img src='<?php echo $product['image']; ?>' />
        </div>
        <div class='name'><?php echo $product['name']; ?></div>
        <div class='price'>$<?php echo $product['price']; ?></div>
        <form method='post' action='<?php echo PAYPAL_URL; ?>'>

        <!-- PayPal business email to collect payments -->
        <input type='hidden' name='business' 
            value='<?php echo PAYPAL_EMAIL; ?>'>

        <!-- Details of item that customers will purchase -->
        <input type='hidden' name='item_number' 
            value='<?php echo $product['code']; ?>'>
        <input type='hidden' name='item_name'
            value='<?php echo $product['name']; ?>'>
        <input type='hidden' name='amount'
            value='<?php echo $product['price']; ?>'>
        <input type='hidden' name='currency_code' 
            value='<?php echo CURRENCY; ?>'>
        <input type='hidden' name='no_shipping' value='1'>
        
        <!-- PayPal return, cancel & IPN URLs -->
        <input type='hidden' name='return' 
            value='<?php echo RETURN_URL; ?>'>
        <input type='hidden' name='cancel_return' 
            value='<?php echo CANCEL_URL; ?>'>
        <input type='hidden' name='notify_url' 
            value='<?php echo NOTIFY_URL; ?>'>

        <!-- Specify a Pay Now button. -->
        <input type="hidden" name="cmd" value="_xclick">
        <button type='submit' class='pay'>Pay Now</button>
        </form>
		</div>
<?php                 
    }
}
?>

</div>    
</body>
</html>

The code mentioned above will produce the subsequent output.

4. Construct a notify.php file to handle IPN and log payment details in the database

A hand holding a smartphone with augmented reality icons for e-commerce and ratings

Generate a notify.php file and paste the provided code into it. This page will manage all PayPal Instant Payment Notification (IPN) events, validate the data, and insert records into the ‘payment_info’ table.

<?php
require_once('dbclass.php');
/*
Read POST data
reading posted data directly from $_POST causes serialization
issues with array data in POST.
Reading raw POST data from input stream instead.
*/
define("IPN_LOG_FILE", "ipn.log");
$raw_post_data = file_get_contents('php://input');
$raw_post_array = explode('&', $raw_post_data);
$myPost = array();
foreach ($raw_post_array as $keyval) {
	$keyval = explode ('=', $keyval);
	if (count($keyval) == 2)
		$myPost[$keyval[0]] = urldecode($keyval[1]);
}

// Build the body of the verification post request, 
// adding the _notify-validate command.
$req = 'cmd=_notify-validate';
if(function_exists('get_magic_quotes_gpc')) {
	$get_magic_quotes_exists = true;
}
foreach ($myPost as $key => $value) {
	if($get_magic_quotes_exists == true && get_magic_quotes_gpc() == 1) {
		$value = urlencode(stripslashes($value));
	} else {
		$value = urlencode($value);
	}
	$req .= "&$key=$value";
}

/*
Post IPN data back to PayPal using curl to 
validate the IPN data is valid & genuine
Anyone can fake IPN data, if you skip it.
*/
$ch = curl_init(PAYPAL_URL);
if ($ch == FALSE) {
	return FALSE;
}
curl_setopt($ch, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_1_1);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_RETURNTRANSFER,1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $req);
curl_setopt($ch, CURLOPT_SSLVERSION, 6);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 1);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 2);
curl_setopt($ch, CURLOPT_FORBID_REUSE, 1);

/*
This is often required if the server is missing a global cert
bundle, or is using an outdated one.
Please download the latest 'cacert.pem' from 
http://curl.haxx.se/docs/caextract.html
*/
if (LOCAL_CERTIFICATE == TRUE) {
	curl_setopt($ch, CURLOPT_CAINFO, __DIR__ . "/cert/cacert.pem");
}

// Set TCP timeout to 30 seconds
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 30);
curl_setopt($ch, CURLOPT_HTTPHEADER, array(
	'Connection: Close',
	'User-Agent: PHP-IPN-Verification-Script'
));

$res = curl_exec($ch);

// cURL error
if (curl_errno($ch) != 0){
	curl_close($ch);
	exit;
} else {
	curl_close($ch);
}

/* 
 * Inspect IPN validation result and act accordingly 
 * Split response headers and payload, a better way for strcmp 
 */
$tokens = explode("\r\n\r\n", trim($res));
$res = trim(end($tokens));
if (strcmp($res, "VERIFIED") == 0 || strcasecmp($res, "VERIFIED") == 0) {
	// assign posted variables to local variables
	$item_number = $_POST['item_number'];
	$item_name = $_POST['item_name'];
	$payment_status = $_POST['payment_status'];
	$amount = $_POST['mc_gross'];
	$currency = $_POST['mc_currency'];
	$txn_id = $_POST['txn_id'];
	$receiver_email = $_POST['receiver_email'];
	// $payer_email = $_POST['payer_email'];

	// check that receiver_email is your PayPal business email
	if (strtolower($receiver_email) != strtolower(PAYPAL_EMAIL)) {
		error_log(date('[Y-m-d H:i e] ').
			"Invalid Business Email: $req" . PHP_EOL, 3, IPN_LOG_FILE);
		exit();
	}

	// check that payment currency is correct
	if (strtolower($currency) != strtolower(CURRENCY)) {
		error_log(date('[Y-m-d H:i e] '). 
			"Invalid Currency: $req" . PHP_EOL, 3, IPN_LOG_FILE);
		exit();
	}

	//Check Unique Transcation ID
	$db = new DB;
	$db->query("SELECT * FROM `payment_info` WHERE txn_id=:txn_id");
	$db->bind(':txn_id', $txn_id);
	$db->execute();
	$unique_txn_id = $db->rowCount();

	if(!empty($unique_txn_id)) {
		error_log(date('[Y-m-d H:i e] '). 
			"Invalid Transaction ID: $req" . PHP_EOL, 3, IPN_LOG_FILE);
		$db->close();
		exit();
	}else{
		$db->query("INSERT INTO `payment_info`
			(`item_number`, `item_name`, `payment_status`,
				 `amount`, `currency`, `txn_id`)
			VALUES
			(:item_number, :item_name, :payment_status, 
				:amount, :currency, :txn_id)");
		$db->bind(":item_number", $item_number);
		$db->bind(":item_name", $item_name);
		$db->bind(":payment_status", $payment_status);
		$db->bind(":amount", $amount);
		$db->bind(":currency", $currency);
		$db->bind(":txn_id", $txn_id);
		$db->execute();
		/* error_log(date('[Y-m-d H:i e] '). 
		"Verified IPN: $req ". PHP_EOL, 3, IPN_LOG_FILE);
		*/
	} 
	$db->close();
	
} else if (strcmp($res, "INVALID") == 0) {
	//Log invalid IPN messages for investigation
	error_log(date('[Y-m-d H:i e] '). 
		"Invalid IPN: $req" . PHP_EOL, 3, IPN_LOG_FILE);
}
?>

5. Create a cancel.php file for payment cancellation scenarios

Generate a cancel.php file and paste the following code into it. Customers will be redirected to this page if they cancel the payment from the PayPal payment page.

<h1>Sorry! Your PayPal Payment has been cancelled.</h1>

6. Form a return.php file to manage the post-payment process

Illustration of a person working on coding and website maintenance

Generate a return.php file and paste the provided code into it. Customers will be redirected to this page upon successful payment.

<html>
<head>
<title>Payment Confirmed</title>
</head>
<body>
    <div style="width:700px; margin:50 auto;">
        <h1>Your paymeny has been received successfully.<br /> Thank you!</h1>
    </div>
</body>
</html>

7. Design a style.css file to apply custom styles to the web elements

Generate a style.css file and paste the following code into it. This serves as the stylesheet for your index page, ensuring that all products are presented in an appealing manner.

body {
    font-family: Arial, sans-serif;
    line-height: 1.6;
}
.product_wrapper {
	float:left;
	padding: 10px;
	text-align: center;
	}
.product_wrapper:hover {
	box-shadow: 0 0 0 2px #e5e5e5;
	cursor:pointer;
	}
.product_wrapper .name {
	font-weight:bold;
	}
.product_wrapper .pay {
	text-transform: uppercase;
    background: #F68B1E;
    border: 1px solid #F68B1E;
    cursor: pointer;
    color: #fff;
    padding: 8px 40px;
    margin-top: 10px;
}
.product_wrapper .pay:hover {
	background: #f17e0a;
    border-color: #f17e0a;
}

Conclusion

Through the comprehensive step-by-step instructions outlined above, individuals can effortlessly incorporate the PayPal payment gateway into their PHP-based websites. PayPal Payments Standard represents the simplest method for integrating payments, allowing you to enable online payments on your website in as little as a day or just a few hours.

Published On
By Jeffrey Morrison

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