如何在PHP中进行支付宝开发？

<?php
require_once 'AlipaySdk.php';
$outTradeNo = '123456789'; //　您的订单号

$request = new AlipayTradePagePayRequest();
$request->setReturnUrl("http://localhost/callback.php");  //　服务器回调地址
$request->setNotifyUrl("http://localhost/notify.php");  //　支付宝回调地址

$request->setBizContent("{" .
    "    "out_trade_no":"$outTradeNo"," .
    "    "product_code":"FAST_INSTANT_TRADE_PAY"," .
    "    "total_amount":88.88," .
    "    "subject":"test subject"," .
    "    "body":"test body"" .
    "  }");

$response = $aliPay->execute($request);
echo $response;

<?php
$request = new AlipayTradeRefundRequest();
$request->setBizContent("{" .
    "    "out_trade_no":"$outTradeNo"," .   //　订单号
    "    "refund_amount":8.88," .             //　退款金额
    "    "refund_reason":"reason"," .       //　退款原因
    "    "out_request_no":"uniqueRefundId"" .   //　退款单号
    "  }");
$response = $aliPay->execute($request);