1.导入阿里下载的demo包到 根目录/ThinkPHP/Extend/Vendor 改名为Alipay
2.进入 根目录/APP/Conf/config.php 加入

'alipay' =>[
        'app_id' => "",
        //商户私钥
        'merchant_private_key' => "",
        //编码格式
        'charset' => "UTF-8",
        //签名方式
        'sign_type'=>"RSA2",
        //支付宝网关
        'gatewayUrl' => "https://openapi.alipay.com/gateway.do",
        //支付宝公钥,查看地址：https://openhome.alipay.com/platform/keyManage.htm 对应APPID下的支付宝公钥。
        'alipay_public_key' => "",
    ],

3.进入/APP/Common/common.php 加入

function alipay($post,$notify_url,$return_url){
    $config = C('alipay');
    
    $arr=[
        'app_id'=>$config['app_id'],
        'merchant_private_key'=>$config['merchant_private_key'],
        'notify_url'=>$notify_url,
        'return_url'=>$return_url,
        'charset'=>$config['charset'],
        'sign_type'=>$config['sign_type'],
        'gatewayUrl'=>$config['gatewayUrl'],
        'alipay_public_key'=>$config['alipay_public_key']
    ];
    // var_dump($arr);
    // exit();
    // vendor('alipay.AlipayTradeService');
    // vendor('alipay.AlipayTradePagePayContentBuilder');
    Vendor('Alipay.wappay.service.AlipayTradeService');
    Vendor('Alipay.wappay.buildermodel.AlipayTradeWapPayContentBuilder');

    $out_trade_no = trim($post['WIDout_trade_no']);
    $subject = trim($post['WIDsubject']);
    $total_amount = trim($post['WIDtotal_amount']);
    $body = trim($post['WIDbody']);
    $payRequestBuilder = new \AlipayTradeWapPayContentBuilder();
    $payRequestBuilder->setBody($body);
    $payRequestBuilder->setSubject($subject);
    $payRequestBuilder->setTotalAmount($total_amount);
    $payRequestBuilder->setOutTradeNo($out_trade_no);
    $aop = new \AlipayTradeService($arr);
    $response = $aop->wappay($payRequestBuilder, $arr['return_url'], $arr['notify_url']);
    var_dump($response);
}

4.进入支付提交表单页面

public function recharge_post(){
        
        // 支付宝API调用
        $arr=[
            'WIDout_trade_no'=>'2221122121212121212',
            'WIDsubject'=>'在线支付',
            'WIDtotal_amount'=>1,
            'WIDbody'=>'商品名'
        ];
        session('order',$order);
        alipay($arr, 'http://bendi.hioo.cn/ThinkPHP/Extend/Vendor/alipay/notify_url.php', 'http://mitsein.com/alipay.trade.wap.pay-PHP-UTF-8/return_url.php');
        }