PHP与小程序的支付接口对接指南

function createSign($params, $key){
    ksort($params);  //按照参数名ASCII码从小到大排序

    $string = '';
    foreach($params as $k => $v){
        if($v != '' && $k != 'sign'){
            $string .= $k . '=' . $v . '&';
        }
    }

    $string .= 'key=' . $key;
    $string = md5($string);  //签名加密

    return strtoupper($string);  //转换成大写
}

function createUnifiedOrder($mchid, $key, $appid, $openid, $out_trade_no, $total_fee){
    $params = array(
        'appid' => $appid,
        'body' => '商品描述',
        'mch_id' => $mchid,
        'nonce_str' => md5(time()),
        'notify_url' => '支付成功回调地址',
        'openid' => $openid,
        'out_trade_no' => $out_trade_no,
        'spbill_create_ip' => $_SERVER['REMOTE_ADDR'],
        'total_fee' => $total_fee,
        'trade_type' => 'JSAPI'
    );

    //生成签名
    $params['sign'] = createSign($params, $key);

    //将数组转换为XML格式
    $xml = '<xml>';
    foreach($params as $k => $v){
        $xml .= '<' . $k . '>' . $v . '</' . $k . '>';
    }
    $xml .= '</xml>';

    //向微信服务器发送请求
    $url = 'https://api.mch.weixin.qq.com/pay/unifiedorder';
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($ch, CURLOPT_POST, 1);
    curl_setopt($ch, CURLOPT_POSTFIELDS, $xml);

    $response = curl_exec($ch);
    curl_close($ch);

    //解析XML响应
    $result = simplexml_load_string($response);
    $prepay_id = $result->prepay_id;  //获取预支付交易会话标识

    return $prepay_id;
}

function getMiniProgramPayParams($mchid, $key, $appid, $openid, $out_trade_no, $total_fee){
    $prepay_id = createUnifiedOrder($mchid, $key, $appid, $openid, $out_trade_no, $total_fee);

    $params = array(
        'appId' => $appid,
        'timeStamp' => time(),
        'nonceStr' => md5(time()),
        'package' => 'prepay_id=' . $prepay_id,
        'signType' => 'MD5'
    );

    //生成签名
    $params['paySign'] = createSign($params, $key);

    return $params;
}