用支付寶的sdk
服務端SDK

$aop = new AopClient ();
            $aop->gatewayUrl = 'https://openapi.alipay.com/gateway.do';
            $aop->appId = '2018111962265438';
            $aop->rsaPrivateKey = 'thZJL2VT0PlgHCgYEAzwp';//開發(fā)者的私鑰
            $aop->alipayrsaPublicKey='ZvpB';//支付寶的公鑰
            $aop->apiVersion = '1.0';
            $aop->signType = 'RSA2';
            $aop->postCharset='UTF-8';
            $aop->format='json';
//支付必要參數(shù)
        $request = new AlipayTradeCreateRequest ();

        $content = array();
        $content['out_trade_no'] = $order;
        $content['total_amount'] = sprintf('%.2f',$allmoney);
        $content['subject'] = '外賣小吃';
        $content['buyer_id'] = '2088802486734682';
        $content=json_encode($content);
        $request->setBizContent($content);
        $result = $aop->execute($request);
        $responseNode = str_replace(".", "_", $request->getApiMethodName()) . "_response";
        $resultCode = $result->$responseNode->code;
        if(!empty($resultCode)&&$resultCode == 10000){
        echo '成功'
        }

使用支付寶提供的密鑰生成器，這個再創(chuàng)建公鑰的時候有提供下載
密鑰生成器下載地址

這個開發(fā)者的私鑰

rsaPrivateKey

這個是支付寶的公鑰

alipayrsaPublicKey

個人博客