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In this tutorial, I will explain how to do PayPal Payment Integration in PHP. As of now, it is the most popular online American payment system which makes it easy to send and receive money over the internet.

The PayPal provides various ways to send and receive money online, you can directly send money to your friend or family member and you can also make payment to several services on the internet by using PayPal.

It is also most popular online payment gateway, use to accept payments through web and mobile applications.

There are some other popular online payment gateways, if you want to offer multiple payment options to your customer then you can also allow them to make payment using Authorize.Net.

I have shared a separate and detailed tutorial about Authorize.Net payment gateway integration using PHP.

Stripe is also popular payment gateway, learn how to integrate stripe payment gateway using PHP.

PayPal offers several ways to Integrate PayPal Payment Gateway to your website, some of them are listed below:

1. PayPal Payments Standard
2. Checkout
3. Subscriptions & Recurring Payments
4. PayPal Invoicing
5. Payouts

I will focus on PayPal Payments Standard, as it is the most easiest way to integrate PayPal payment using PHP. So lets start integration of PayPal payment standards in PHP.

I will use my previous tutorial PHP CRUD Operations to access database and perform all database related operations using class dbclass.php.

I will skip rewriting of the same class to avoid duplication of code. However, I will include the same class in download file, so you do not need to worry about the dbclass.php class.

Steps to Integration PayPal Payment Gateway using PHP

I will follow the below steps to integrate PayPal payment gateway on my website using PHP.

1. Create a Database, Tables and Dump Sample Data
2. Create a config.php File & Make Necessary Changes
3. Create an index.php File & Display Some Products to Buy
4. Create a notify.php File, Handle IPN & Insert Payment Record in DB
5. Create a cancel.php File
6. Create a return.php File
7. Create a style.css File

1. Create a Database, Tables and Dump Sample Data

To create database run the following query in MySQL.

CREATE DATABASE allphptricks;

To create the tables run 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;

Note: I have already attached the SQL file of this table with dummy data, just download the complete zip file of 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;

Dump sample data into `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 & Make Necessary Changes

Create a config.php file, copy paste the following code and make necessary changes like update your database credentials, database name, username, password, also update your PayPal business email, return, cancel, notify URLs etc.

<?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. Create an index.php File & Display Some Products to Buy

Create an index.php file, copy paste the following code in it. This page will display all products from `products` table, so that user can easily buy any product.

<?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 above code will generate the following output.

4. Create a notify.php File, Handle IPN & Insert Payment Record in DB

Create a notify.php file, copy paste the following code in it. This page will handle all PayPal Instant Payment Notification (IPN), validate the data and add record into `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

Create a cancel.php file, copy paste the following code in it. Customer will be redirected here if he/she cancels payment from PayPal payment page.

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

6. Create a return.php File

Create a return.php file, copy paste the following code in it. Customer will be redirected here when the payment is successful.

<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. Create a style.css File

Create a style.css file, copy paste the following code in it. This is the stylesheet of your index page where all products are displayed nicely.

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

By following the above step by step guide, anyone can easily integrate PayPal payment gateway in PHP. PayPal Payments Standard is the easiest payment integration which can enable online payment on your website within a day or in a few hours.

I try to keep my code easy and simple as possible, but if anyone of you still having any trouble so feel free to comment below, I try my best to reply all comments and questions of my blog readers.

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