步骤一：注册账号（个人账号）

https://www.paypal.com/us/home#/pattern/confirm

步骤二：创建沙箱账号，用申请的账号登录地址：

https://developer.paypal.com/developer/accounts/

显示的页面

获取测试登录账号和密码。

步骤三：登录沙箱账号（沙箱账号，只能在沙箱地址上登录；主账号不能在沙箱地址上登录）：

https://www.sandbox.paypal.com/c2/signin?country.x=C2&locale.x=zh_C2

步骤四：获取沙箱Client ID和Secret。用主账号登录：

https://developer.paypal.com/developer/applications/

创建App：

创建App

步骤五：在我的项目安装paypal支付源码，可以直接composer安装：

composer require "paypal/rest-api-sdk-php:*"

参考官方安装地址：

https://github.com/paypal/PayPal-PHP-SDK/wiki

步骤六：创建服务端checkout，能访问：

<?php
// 1. Autoload the SDK Package. This will include all the files and classes to your autoloader
// Used for composer based installation
require __DIR__  . '/vendor/autoload.php';
// Use below for direct download installation
// require __DIR__  . '/PayPal-PHP-SDK/autoload.php';

// After Step 1
$apiContext = new \PayPal\Rest\ApiContext(
        new \PayPal\Auth\OAuthTokenCredential(
            'AYSq3RDGsmBLJE-otTkBtM-jBRd1TCQwFf9RGfwddNXWz0uFU9ztymylOhRS',     // ClientID
            'EGnHDxD_qRPdaLdZz8iCr8N7_MzF-YHPTkjs6NKYQvQSBngp4PTTVWkPZRbL'      // ClientSecret
        )
);

// After Step 2
$payer = new \PayPal\Api\Payer();
$payer->setPaymentMethod('paypal');

$amount = new \PayPal\Api\Amount();
$amount->setTotal('1.00');
$amount->setCurrency('USD');

$transaction = new \PayPal\Api\Transaction();
$transaction->setAmount($amount);

$redirectUrls = new \PayPal\Api\RedirectUrls();
$redirectUrls->setReturnUrl("https://example.com/your_redirect_url.html")//执行付款
    ->setCancelUrl("https://example.com/your_cancel_url.html");//取消付款

$payment = new \PayPal\Api\Payment();
$payment->setIntent('sale')
    ->setPayer($payer)
    ->setTransactions(array($transaction))
    ->setRedirectUrls($redirectUrls);

// After Step 3
try {
    $payment->create($apiContext);
    echo $payment;

    echo "\n\nRedirect user to approval_url: " . $payment->getApprovalLink() . "\n";
}
catch (\PayPal\Exception\PayPalConnectionException $ex) {
    // This will print the detailed information on the exception.
    //REALLY HELPFUL FOR DEBUGGING
    echo $ex->getData();
}
$approvalUrl = $payment->getApprovalLink();
header("Location: {$approvalUrl}");

执行以上代码最终会跳出，期间会需要登录，就是你创建的buyer@账号：

1

2

3

步骤七：执行付款 注意步骤六的执行付款注释及其对应的url：

<?php

// # Create Payment using PayPal as payment method
// This sample code demonstrates how you can process a 
// PayPal Account based Payment.
// API used: /v1/payments/payment

require __DIR__  . '/vendor/autoload.php';
use PayPal\Api\Amount;
use PayPal\Api\Details;
use PayPal\Api\Item;
use PayPal\Api\ItemList;
use PayPal\Api\Payer;
use PayPal\Api\Payment;
use PayPal\Api\RedirectUrls;
use PayPal\Api\Transaction;

// ### Payer
// A resource representing a Payer that funds a payment
// For paypal account payments, set payment method
// to 'paypal'.
$payer = new Payer();
$payer->setPaymentMethod("paypal");

// ### Itemized information
// (Optional) Lets you specify item wise
// information
$item1 = new Item();
$item1->setName('Ground Coffee 40 oz')
    ->setCurrency('USD')
    ->setQuantity(1)
    ->setSku("123123") // Similar to `item_number` in Classic API
    ->setPrice(7.5);
$item2 = new Item();
$item2->setName('Granola bars')
    ->setCurrency('USD')
    ->setQuantity(5)
    ->setSku("321321") // Similar to `item_number` in Classic API
    ->setPrice(2);

$itemList = new ItemList();
$itemList->setItems(array($item1, $item2));

// ### Additional payment details
// Use this optional field to set additional
// payment information such as tax, shipping
// charges etc.
$details = new Details();
$details->setShipping(1.2)
    ->setTax(1.3)
    ->setSubtotal(17.50);

// ### Amount
// Lets you specify a payment amount.
// You can also specify additional details
// such as shipping, tax.
$amount = new Amount();
$amount->setCurrency("USD")
    ->setTotal(20)
    ->setDetails($details);

// ### Transaction
// A transaction defines the contract of a
// payment - what is the payment for and who
// is fulfilling it. 
$transaction = new Transaction();
$transaction->setAmount($amount)
    ->setItemList($itemList)
    ->setDescription("Payment description")
    ->setInvoiceNumber(uniqid());

// ### Redirect urls
// Set the urls that the buyer must be redirected to after 
// payment approval/ cancellation.
$baseUrl = getBaseUrl();
$redirectUrls = new RedirectUrls();
$redirectUrls->setReturnUrl("$baseUrl/ExecutePayment.php?success=true")
    ->setCancelUrl("$baseUrl/ExecutePayment.php?success=false");

// ### Payment
// A Payment Resource; create one using
// the above types and intent set to 'sale'
$payment = new Payment();
$payment->setIntent("sale")
    ->setPayer($payer)
    ->setRedirectUrls($redirectUrls)
    ->setTransactions(array($transaction));


// For Sample Purposes Only.
$request = clone $payment;

// ### Create Payment
// Create a payment by calling the 'create' method
// passing it a valid apiContext.
// (See bootstrap.php for more on `ApiContext`)
// The return object contains the state and the
// url to which the buyer must be redirected to
// for payment approval
try {
    $payment->create($apiContext);
} catch (Exception $ex) {
    // NOTE: PLEASE DO NOT USE RESULTPRINTER CLASS IN YOUR ORIGINAL CODE. FOR SAMPLE ONLY
    ResultPrinter::printError("Created Payment Using PayPal. Please visit the URL to Approve.", "Payment", null, $request, $ex);
    exit(1);
}

// ### Get redirect url
// The API response provides the url that you must redirect
// the buyer to. Retrieve the url from the $payment->getApprovalLink()
// method
$approvalUrl = $payment->getApprovalLink();

// NOTE: PLEASE DO NOT USE RESULTPRINTER CLASS IN YOUR ORIGINAL CODE. FOR SAMPLE ONLY
 ResultPrinter::printResult("Created Payment Using PayPal. Please visit the URL to Approve.", "Payment", "<a href='$approvalUrl' >$approvalUrl</a>", $request, $payment);

return $payment;

步骤八：配置回调数据验证notify，登录主账号：

1

2

注意：必须使用https，否则创建失败。

步骤九：验证数据：

<?php

$content = file_get_contents("php://input");
if(!empty($content)){
     $verify = $this->verifyNotify($content);
     if ($verify) {
           return true;
     }else{
          return  false;
     }
 }else{
  return false;
}

function verifyNotify($post)
{
 if(empty($post)){
      return false;
}
$post = json_decode($post, true);
/**
  * completed 表示订单状态ok. 这里怕是伪造的数据。去paypal服务器上去查
  */
if ($post['resource']['state'] != 'completed') {
      return false;
}
/**
  * invoice_number,【在客户端（ios或安卓）】发起支付的时候加入进去的。如果这个数据是空的，客户端配置有问题。
  * 【客户端请求服务器，自己生成的唯一订单号，给客户端，客户端再加入到palpal支付参数里边】
  * 收取订单号
  */
$saleId = $post['resource']['sale_id'] ?: $post['resource']['id'];
//查询订单
$apiContext = $this->getApiContext();
try{
            $sale = Sale::get($saleId, $apiContext);
            $orderId = $sale->invoice_number;//$post['resource']['invoice_number'] 订单号
            $st = $sale->getState();
            if($st == 'completed'){
                //付款类型COMPLETED
                //验证成功之后的逻辑。
                return true;
            } elseif($st == 'reversed'){
                //REVERSED  PayPal reverses a sale
               //更新数据 用户申请退款，paypal官方介入
            }else{
                return false;
            }
        }catch (\Exception $ex){
            //抛出异常。
            return false;
        }

}

Tips：
Paypal安装教程：

https://github.com/paypal/PayPal-PHP-SDK/wiki

REST API Samples 地址：

http://paypal.github.io/PayPal-PHP-SDK/sample/

销售状态码：

https://developer.paypal.com/docs/integration/direct/webhooks/event-names/#sales

paypal开发者文档（这里使用的checkout文档）：

https://developer.paypal.com/docs/

在使用checkout api文档的时候，最好是用搜索找东西：

https://developer.paypal.com/docs/api/overview/

使用文档的一个小例子,比如使用以下地址：

https://developer.paypal.com/docs/api/payments/v1/

如果右侧的代码上边有这些按钮：

image.png

可以点击进去看看示例代码。

paypal IPN通知：

https://developer.paypal.com/docs/notifications/#ipn?mark=ipn