Guide to Integrating WeChat Mobile Payment (WeChat Pay) for Android and iOS

This article provides a step‑by‑step guide for applying, configuring, and integrating WeChat Mobile Payment (WeChat Pay) on both Android and iOS platforms.

1. Application – Follow the official documentation to apply for the Open Platform and the Merchant Platform. After approval you obtain AppID, AppSecret, mch_id, API key and merchant certificates.

2. Integration Process – The main flow includes unified order, generating signed payment parameters on the server, invoking the client SDK, and handling asynchronous payment notifications.

2.1 Unified Order (PHP example)

$appid = "";  //你的appid
$mch_id = "";  //商户id
$wx_api_key = "";    //商户api秘钥
$out_trade_no = "";  //自己业务系统生成的交易no，可以唯一标识
$client_ip = "";  //客户端ip
$notify_url = "";    //接收支付结果通知url

$UNIFIED_ORDER_URL = "https://api.mch.weixin.qq.com/pay/unifiedorder";  //统一下单地址

$data = array();
$data['appid'] = $appid; 
$data['mch_id'] =$mch_id;
$data['nonce_str'] = randomStr(20);  //随机20位字符串
$data['body'] = "微信移动支付测试";
$data['detail'] = "微信移动支付测试";
$data['out_trade_no'] = $out_trade_no;    
$data['total_fee'] = 1;  //注意 单位是分
$data['spbill_create_ip'] = $client_ip;
$data['notify_url'] = $notify_url;
$data['trade_type'] = "APP";  //交易类型
$data['sign'] =sign($data, $wx_api_key);    //签名

//转为xml格式
$xml_str = arrayToXmlStr($data); 

//发送请求 使用封装好的curl_post
$result = curl_post($UNIFIED_ORDER_URL, $xml_str);

//解析得到的值
$get_data = simplexml_load_string($raw_data, 'SimpleXMLElement', LIBXML_NOCDATA);
$get_para = array();
$get_sign = "";
foreach ($get_data->children() as $child) 
{    
    if($child->getName() == 'sign') {            
        $get_sign = strval($child);    
    } else {            
        $get_para[strval($child->getName())] = strval($child);    
    }
}

if($get_para['return_code'] !== "SUCCESS") {
    //return code fail
}

//验证签名
if(!verifySign($get_sign, $get_para, $wx_api_key)) {
    //验证签名非法
}

//可以自行处理解析获得的参数
//todo...

2.2 Generating Payment Parameters

//生成支付参数
$data = array();
$data['appid'] = $appid; 
$data['mch_id'] =$mch_id;
$data['prepayid'] = $prepayid;    //刚才统一下单生成的prepayid
$data['package'] = "Sign=WXPay";
$data['noncestr'] = randomStr(20);
$data['timestamp'] = time();
$data['sign'] =sign($data, $wx_api_key);

$pay_param = json_encode($data);

3. Calling Payment

Android – Use a custom Android SDK (GitHub: https://github.com/tsy12321/PayAndroid). Ensure the package name and signing certificate match the values entered in the Open Platform; the app must be signed when testing.

iOS – Use a custom iOS SDK (GitHub: https://github.com/tsy12321/PayiOS).

4. Asynchronous Result Notification

$raw_data = $GLOBALS["HTTP_RAW_POST_DATA"];

$get_data = simplexml_load_string($raw_data, 'SimpleXMLElement', LIBXML_NOCDATA);
$get_para = array();
$get_sign = "";
foreach ($get_data->children() as $child) 
{    
    if($child->getName() == 'sign') {            
        $get_sign = strval($child);    
    } else {            
        $get_para[strval($child->getName())] = strval($child);    
    }
}

if($get_para['return_code'] !== "SUCCESS") {
    //return code fail
    die("
FAIL
");
}

//验证签名
if(!verifySign($get_sign, $get_para, $wx_api_key)) {
    //验证签名非法
    //todo
    die("
FAIL
");
}

//在这其实通知已经接受成功 可以返回成功告诉微信不用再次通知了
echo("
SUCCESS
");

//业务状态码判断
if ($get_para['result_code'] !== 'SUCCESS') {        
    //状态码错误
    //支付错误 更改订单状态 记录log等 
    //...
}

//支付成功 更改订单状态 记录log等 
//todo

Important notes: verify signatures, handle duplicate notifications, and confirm final status on the server.

5. Other Recommendations

After receiving a synchronous result on the client, periodically poll the server for the final status; the server’s result is authoritative.