微信小程序云开发开放了http api，可以从第三方访问云服务了。方便很多。云服务的后台，可以用PC端写了。
流程大概就是通过appid,appkey获得access_token,这个access_token一定要在有效期内自己备份，不要每次使用都去申请，因为企鹅那边永远是是你的appid申请的最后一次的access_token有效。多此申请可能造成前面业务失败。我这里用redis存储申请到的access_token,正好还可以设置超时时间。
获取access_token的链接如下：

$url = "https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid=".APPID."&secret=".APPKEY;

获取access_token后，可以用云环境ID访问自己小程序中的云资源了。比如查询云数据库：

    $url = "https://api.weixin.qq.com/tcb/databasequery?access_token=".$at;
    $data = array ('env' => APPCLOUDID,'query'=>'db.collection("member").where({"comp.review":1}).get()');
    $data = json_encode($data);
    $opts = array (
        'http' => array (
            'method' => 'POST',
            'header'=> "Content-type: application/jsonrn",
            "Content-Length: " . strlen($data) . "rn",
            'content' => $data
        )
    );
    
    $context = stream_context_create($opts);
    $html = file_get_contents($url, false, $context);
    //var_dump($html);
    $arr["data"] = $html;

下面是完整的php代码。
minip.php如下：

<?php
require_once(dirname(__FILE__).'/../../config.php');


$minip_actions = array(
    'comp-review-get' => function($param,&$arr,$token,$at){
        $arr["status"] = 0;
        $arr["msg"] = "callminip";        
        compreviewget($param,$arr,$token,$at);
    },
);

function compreviewget ($param,&$arr,$token,$at){
    $url = "https://api.weixin.qq.com/tcb/databasequery?access_token=".$at;
    $data = array ('env' => APPCLOUDID,'query'=>'db.collection("member").where({"comp.review":1}).get()');
    $data = json_encode($data);
    $opts = array (
        'http' => array (
            'method' => 'POST',
            'header'=> "Content-type: application/jsonrn",
            "Content-Length: " . strlen($data) . "rn",
            'content' => $data
        )
    );
    
    $context = stream_context_create($opts);
    $html = file_get_contents($url, false, $context);
    //var_dump($html);
    $arr["data"] = $html;
}

function callMiniP($param,&$arr,$token){
    global $minip_actions;
    $redis = new Redis();
    $redis->connect(DB_REDIS_IP, 6379);
    $redis->auth(DB_REDIS_PWD);
    $key = '6Xdd55klotnbpo98_minip_access_token';
    $ui = $redis->get($key);
    $from = '';
    if($ui==False){/// access_token已经失效。需要重新申请。
        do{
            $url = "https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid=".APPID."&secret=".APPKEY;
            $j =json_decode( file_get_contents($url),false);//true,转化成数组
            if(property_exists($j, 'errcode')){
                if($j->errcode == -1){
                    continue;
                }else if($j->errcode > 0){
                break;
                }
            }
            $redis->select(0);
            $count = 0;
            $redis->set($key, serialize($j), ['nx', 'ex'=>$j->expires_in]);
            $ui0 = $j;
            $from = "QQ";
            break;
        }while(true);
    }else{
        $ui0 = unserialize($ui);
        $from = "local";
    }
    if(!property_exists($ui0, 'access_token')){
        return;
    }
    
    $action = $param["action"];
    $arr["msg"] = "1未知action: ".$action;
    if(!array_key_exists($action,$minip_actions)){
        return;
    }
    $func = $minip_actions[$action];
    $func($param,$arr,$token,$ui0->access_token);
    return;
}

?>