In this article, we will learn how to integrate Paypal with Codeigniter. You will also learn, after successful payment, it stores transaction data into the database table.



Database Structure

Copy the following code and import it in your database

-- phpMyAdmin SQL Dump
-- version 5.0.4
-- https://www.phpmyadmin.net/
--
-- Host: 127.0.0.1
-- Generation Time: Jan 25, 2021 at 12:52 AM
-- Server version: 10.4.17-MariaDB
-- PHP Version: 7.3.25

SET SQL_MODE = "NO_AUTO_VALUE_ON_ZERO";
START TRANSACTION;
SET time_zone = "+00:00";


/*!40101 SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT */;
/*!40101 SET @OLD_CHARACTER_SET_RESULTS=@@CHARACTER_SET_RESULTS */;
/*!40101 SET @OLD_COLLATION_CONNECTION=@@COLLATION_CONNECTION */;
/*!40101 SET NAMES utf8mb4 */;

--
-- Database: `paymentgateway`
--

-- --------------------------------------------------------

--
-- Table structure for table `payments`
--

CREATE TABLE `payments` (
  `payment_id` int(11) NOT NULL,
  `user_id` int(11) NOT NULL,
  `product_id` int(11) NOT NULL,
  `txn_id` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
  `payment_gross` float(10,2) NOT NULL,
  `currency_code` varchar(5) COLLATE utf8_unicode_ci NOT NULL,
  `payer_email` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
  `payment_status` varchar(255) COLLATE utf8_unicode_ci NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;

-- --------------------------------------------------------

--
-- Table structure for table `products`
--

CREATE TABLE `products` (
  `id` int(11) NOT NULL,
  `name` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
  `price` float(10,2) NOT NULL,
  `status` tinyint(1) NOT NULL DEFAULT 1
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;

--
-- Dumping data for table `products`
--

INSERT INTO `products` (`id`, `name`, `price`, `status`) VALUES
(1, 'New Apple iPhone 12 Pro (256GB) - Graphite', 700.00, 1),
(2, 'Samsung Galaxy M51', 250.00, 1);

--
-- Indexes for dumped tables
--

--
-- Indexes for table `payments`
--
ALTER TABLE `payments`
  ADD PRIMARY KEY (`payment_id`);

--
-- Indexes for table `products`
--
ALTER TABLE `products`
  ADD PRIMARY KEY (`id`);

--
-- AUTO_INCREMENT for dumped tables
--

--
-- AUTO_INCREMENT for table `payments`
--
ALTER TABLE `payments`
  MODIFY `payment_id` int(11) NOT NULL AUTO_INCREMENT;

--
-- AUTO_INCREMENT for table `products`
--
ALTER TABLE `products`
  MODIFY `id` int(11) NOT NULL AUTO_INCREMENT, AUTO_INCREMENT=3;
COMMIT;

/*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */;
/*!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS */;
/*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */;


Show the dummy products with prices

Create Product controller file inside application/controller and put the following code

application/controllers/
┣ Products.php

<?php
defined('BASEPATH') OR exit('No direct script access allowed');

class Products extends CI_Controller {
	function  __construct() {
        parent::__construct();
        $this->load->library('paypal_lib');
        $this->load->model('product');
    }
    
    function index(){
        $data = array();
        //get products data from database
        $data['products'] = $this->product->getRows();
        //pass the products data to view
        $this->load->view('products/index', $data);
    }

    function buy($id){
        //Set variables for paypal form
        $returnURL = base_url().'paypal/success'; //payment success url
        $cancelURL = base_url().'paypal/cancel'; //payment cancel url
        $notifyURL = base_url().'paypal/ipn'; //ipn url
        //get particular product data
        $product = $this->product->getRows($id);
        $userID = 1; //current user id
        $logo = base_url().'assets/images/logo.png';

        
        $this->paypal_lib->add_field('return', $returnURL);
        $this->paypal_lib->add_field('cancel_return', $cancelURL);
        $this->paypal_lib->add_field('notify_url', $notifyURL);
        $this->paypal_lib->add_field('item_name', $product['name']);
        $this->paypal_lib->add_field('custom', $userID);
        $this->paypal_lib->add_field('item_number',  $product['id']);
        $this->paypal_lib->add_field('amount',  $product['price']);        
        $this->paypal_lib->image($logo);
        
        $this->paypal_lib->paypal_auto_form();
    }
}


Setting up Paypal Button

Create Paypal controller file inside application/controller and put the following code

application/controllers/
┣ Paypal.php

<?php

if (!defined('BASEPATH'))
    exit('No direct script access allowed');

class Paypal extends CI_Controller {

    function __construct() {
        parent::__construct();
        $this->load->library('paypal_lib');
        $this->load->model('product');
    }

    function success() {
        //get the transaction data
        $paypalInfo = $this->input->get();

        $data['item_number'] = $paypalInfo['item_number'];
        $data['txn_id'] = $paypalInfo["tx"];
        $data['payment_amt'] = $paypalInfo["amt"];
        $data['currency_code'] = $paypalInfo["cc"];
        $data['status'] = $paypalInfo["st"];

        //pass the transaction data to view
        $this->load->view('paypal/success', $data);
    }

    function cancel() {
        $this->load->view('paypal/cancel');
    }

    function ipn() {
        //paypal return transaction details array
        $paypalInfo = $this->input->post();

        $data['user_id'] = $paypalInfo['custom'];
        $data['product_id'] = $paypalInfo["item_number"];
        $data['txn_id'] = $paypalInfo["txn_id"];
        $data['payment_gross'] = $paypalInfo["payment_gross"];
        $data['currency_code'] = $paypalInfo["mc_currency"];
        $data['payer_email'] = $paypalInfo["payer_email"];
        $data['payment_status'] = $paypalInfo["payment_status"];

        $paypalURL = $this->paypal_lib->paypal_url;
        $result = $this->paypal_lib->curlPost($paypalURL, $paypalInfo);

        //check whether the payment is verified
        if (preg_match("/VERIFIED/i", $result)) {
            //insert the transaction data into the database
            $this->product->insertTransaction($data);
        }
    }

}

?>


Create Views to show products, cancel Payment, success Payment

structure of the view file and create one by one

application/views/
┣ paypal/
┃ ┣ cancel.php
┃ ┗ success.php
┣ products/
┃ ┗ index.php

paypal/cancel.php

<h3>Payment cancelled</h3>


paypal/success.php

<div>
    <h2>Your payment was successful, thank you for purchase.</h2>
    <p>Item Number :<?php echo $item_number; ?></p>
    <p>TXN ID: <?php echo $txn_id; ?></p>
    <p>Amount Paid :  <strong>$<?php echo $payment_amt . ' ' . $currency_code; ?></strong></p>
    <p>Payment Status : <strong><?php echo $status; ?></strong></p>
</div>


products/index.php

<h1>My Shop</h1>
<?php if (!empty($products)): foreach ($products as $product): ?>
        <div>
            <h2><?php echo $product['name']; ?></h2>
            <p>$<?php echo $product['price']; ?> USD</hp>
        </div>
        <a href="<?php echo base_url() . 'products/buy/' . $product['id']; ?>">
            Pay via PayPal
        </a>

        <div style="border-bottom: 1px solid #ccc;margin: 20px;"></div>

    <?php endforeach; ?>
<?php endif; ?>


Paypal Configuration 

Create paypal configuration file paypallib_config.php to enable sandbox and live payment

application/config/
┣ paypallib_config.php


paypallib_config.php

<?php  if (!defined('BASEPATH')) exit('No direct script access allowed');

// ------------------------------------------------------------------------
// Paypal IPN Class
// ------------------------------------------------------------------------

// Use PayPal on Sandbox or Live
$config['sandbox'] = TRUE; // FALSE for live environment

// PayPal Business Email ID
$config['business'] = 'gajanand.kgn@gmail.com';

// If (and where) to log ipn to file
$config['paypal_lib_ipn_log_file'] = BASEPATH . 'logs/paypal_ipn.log';
$config['paypal_lib_ipn_log'] = TRUE;

// Where are the buttons located at 
$config['paypal_lib_button_path'] = 'buttons';

// What is the default currency?
$config['paypal_lib_currency_code'] = 'USD';

?>

Create your own library file 

libraries/
┗ Paypal_lib.php

Paypal_lib.php

<?php if (!defined('BASEPATH')) exit('No direct script access allowed'); 
/**
 * Code Igniter
 *
 * An open source application development framework for PHP 4.3.2 or newer
 *
 * @package		CodeIgniter
 * @author		Rick Ellis
 * @copyright	Copyright (c) 2006, pMachine, Inc.
 * @license		http://www.codeignitor.com/user_guide/license.html
 * @link		http://www.codeigniter.com
 * @since		Version 1.0
 * @filesource
 */

// ------------------------------------------------------------------------

/**
 * PayPal_Lib Controller Class (Paypal IPN Class)
 *
 * This CI library is based on the Paypal PHP class by Micah Carrick
 * See www.micahcarrick.com for the most recent version of this class
 * along with any applicable sample files and other documentaion.
 *
 * This file provides a neat and simple method to interface with paypal and
 * The paypal Instant Payment Notification (IPN) interface.  This file is
 * NOT intended to make the paypal integration "plug 'n' play". It still
 * requires the developer (that should be you) to understand the paypal
 * process and know the variables you want/need to pass to paypal to
 * achieve what you want.  
 *
 * This class handles the submission of an order to paypal as well as the
 * processing an Instant Payment Notification.
 * This class enables you to mark points and calculate the time difference
 * between them.  Memory consumption can also be displayed.
 *
 * The class requires the use of the PayPal_Lib config file.
 */

// ------------------------------------------------------------------------

class paypal_lib {

	var $last_error;			// holds the last error encountered
	var $ipn_log;				// bool: log IPN results to text file?

	var $ipn_log_file;			// filename of the IPN log
	var $ipn_response;			// holds the IPN response from paypal	
	var $ipn_data = array();	// array contains the POST values for IPN
	var $fields = array();		// array holds the fields to submit to paypal

	var $submit_btn = '';		// Image/Form button
	var $button_path = '';		// The path of the buttons
	
	var $CI;
	
	function __construct()
	{
		$this->CI =& get_instance();
		$this->CI->load->helper('url');
		$this->CI->load->helper('form');
		$this->CI->load->config('paypallib_config');
		
		$sanbox = $this->CI->config->item('sandbox');
		$this->paypal_url = ($sanbox == TRUE)?'https://www.sandbox.paypal.com/cgi-bin/webscr':'https://www.paypal.com/cgi-bin/webscr';
                
		$this->last_error = '';
		$this->ipn_response = '';

		$this->ipn_log_file = $this->CI->config->item('paypal_lib_ipn_log_file');
		$this->ipn_log = $this->CI->config->item('paypal_lib_ipn_log'); 
		
		$this->button_path = $this->CI->config->item('paypal_lib_button_path');
		
		// populate $fields array with a few default values.  See the paypal
		// documentation for a list of fields and their data types. These defaul
		// values can be overwritten by the calling script.
		$businessEmail = $this->CI->config->item('business');
		$this->add_field('business',$businessEmail);
		$this->add_field('rm','2');			  // Return method = POST
		$this->add_field('cmd','_xclick');

		$this->add_field('currency_code', $this->CI->config->item('paypal_lib_currency_code'));
	    $this->add_field('quantity', '1');
		$this->button('Pay Now!');
	}

	function button($value)
	{
		// changes the default caption of the submit button
		$this->submit_btn = form_submit('pp_submit', $value);
	}

	function image($file)
	{
		$this->submit_btn = '<input type="image" name="add" src="' . site_url($this->button_path .'/'. $file) . '" border="0" />';
	}


	function add_field($field, $value) 
	{
		// adds a key=>value pair to the fields array, which is what will be 
		// sent to paypal as POST variables.  If the value is already in the 
		// array, it will be overwritten.
		$this->fields[$field] = $value;
	}

	function paypal_auto_form() 
	{
		// this function actually generates an entire HTML page consisting of
		// a form with hidden elements which is submitted to paypal via the 
		// BODY element's onLoad attribute.  We do this so that you can validate
		// any POST vars from you custom form before submitting to paypal.  So 
		// basically, you'll have your own form which is submitted to your script
		// to validate the data, which in turn calls this function to create
		// another hidden form and submit to paypal.

		$this->button('Click here if you\'re not automatically redirected...');

		echo '<html>' . "\n";
		echo '<head><title>Processing Payment...</title></head>' . "\n";
		echo '<body style="text-align:center;" onLoad="document.forms[\'paypal_auto_form\'].submit();">' . "\n";
		echo '<p style="text-align:center;">Please wait, your order is being processed and you will be redirected to the paypal website.</p>' . "\n";
		echo $this->paypal_form('paypal_auto_form');
		echo '</body></html>';
	}

	function paypal_form($form_name='paypal_form') 
	{
		$str = '';
		$str .= '<form method="post" action="'.$this->paypal_url.'" name="'.$form_name.'"/>' . "\n";
		foreach ($this->fields as $name => $value)
			$str .= form_hidden($name, $value) . "\n";
		$str .= '<p>'. $this->submit_btn . '</p>';
		$str .= form_close() . "\n";

		return $str;
	}
	
	function validate_ipn()
	{
		// parse the paypal URL
		$url_parsed = parse_url($this->paypal_url);		  

		// generate the post string from the _POST vars aswell as load the
		// _POST vars into an arry so we can play with them from the calling
		// script.
		$post_string = '';	 
		if ($this->CI->input->post())
		{
			foreach ($this->CI->input->post() as $field=>$value)
			{ 
				$this->ipn_data[$field] = $value;
				$post_string .= $field.'='.urlencode(stripslashes($value)).'&'; 
			}
		}
		
		$post_string.="cmd=_notify-validate"; // append ipn command

		// open the connection to paypal
		$fp = fsockopen($url_parsed['host'],"80",$err_num,$err_str,30); 
		if(!$fp)
		{
			// could not open the connection.  If loggin is on, the error message
			// will be in the log.
			$this->last_error = "fsockopen error no. $errnum: $errstr";
			$this->log_ipn_results(false);		 
			return false;
		} 
		else
		{ 
			// Post the data back to paypal
			fputs($fp, "POST $url_parsed[path] HTTP/1.1\r\n"); 
			fputs($fp, "Host: $url_parsed[host]\r\n"); 
			fputs($fp, "Content-type: application/x-www-form-urlencoded\r\n"); 
			fputs($fp, "Content-length: ".strlen($post_string)."\r\n"); 
			fputs($fp, "Connection: close\r\n\r\n"); 
			fputs($fp, $post_string . "\r\n\r\n"); 

			// loop through the response from the server and append to variable
			while(!feof($fp))
				$this->ipn_response .= fgets($fp, 1024); 

			fclose($fp); // close connection
		}

		if (preg_match("/VERIFIED/",$this->ipn_response))
		{
			// Valid IPN transaction.
			$this->log_ipn_results(true);
			return true;		 
		} 
		else 
		{
			// Invalid IPN transaction.  Check the log for details.
			$this->last_error = 'IPN Validation Failed.';
			$this->log_ipn_results(false);	
			return false;
		}
	}

	function log_ipn_results($success) 
	{
		if (!$this->ipn_log) return;  // is logging turned off?

		// Timestamp
		$text = '['.date('m/d/Y g:i A').'] - '; 

		// Success or failure being logged?
		if ($success) $text .= "SUCCESS!\n";
		else $text .= 'FAIL: '.$this->last_error."\n";

		// Log the POST variables
		$text .= "IPN POST Vars from Paypal:\n";
		foreach ($this->ipn_data as $key=>$value)
			$text .= "$key=$value, ";

		// Log the response from the paypal server
		$text .= "\nIPN Response from Paypal Server:\n ".$this->ipn_response;

		// Write to log
		$fp=fopen($this->ipn_log_file,'a');
		fwrite($fp, $text . "\n\n"); 

		fclose($fp);  // close file
	}


	function dump() 
	{
		// Used for debugging, this function will output all the field/value pairs
		// that are currently defined in the instance of the class using the
		// add_field() function.

		ksort($this->fields);
		echo '<h2>ppal->dump() Output:</h2>' . "\n";
		echo '<code style="font: 12px Monaco, \'Courier New\', Verdana, Sans-serif;  background: #f9f9f9; border: 1px solid #D0D0D0; color: #002166; display: block; margin: 14px 0; padding: 12px 10px;">' . "\n";
		foreach ($this->fields as $key => $value) echo '<strong>'. $key .'</strong>:	'. urldecode($value) .'<br/>';
		echo "</code>\n";
	}
	
	
	function curlPost($paypalurl,$paypalreturnarr)
	{
		
		$req = 'cmd=_notify-validate';
		foreach($paypalreturnarr as $key => $value) 
		{
			$value = urlencode(stripslashes($value));
			$req .= "&$key=$value";
		}
			
		$ipnsiteurl=$paypalurl;
		$ch = curl_init();
		curl_setopt($ch, CURLOPT_URL, $ipnsiteurl);
		curl_setopt($ch, CURLOPT_HEADER, false);
		curl_setopt($ch, CURLOPT_POST, 1);
		curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
		curl_setopt($ch, CURLOPT_POSTFIELDS, $req);
		$result = curl_exec($ch);
		curl_close($ch);
	
		return $result;
	}
	
	

}

?>


Output:


it will redirect you to PayPal to pay



After a successful transaction, it will save your transaction data in a database table