Complete CodeIgniter 3 to 4 Migration | Generated by AI

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Question: How do I continue the CodeIgniter 3 to CodeIgniter 4 migration, specifically rewriting JSSDK.php and fixing the remaining blockers?

Answer:

Here’s a comprehensive step-by-step guide to tackle the remaining migration work:

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CI3 → CI4 Migration: Completing the Refactor

Step 1: Rewrite JSSDK.php for CI4

The core pattern change: replace get_instance() and CI3 loaders with constructor injection.

<?php
// app/Libraries/JSSDK.php

namespace App\Libraries;

use CodeIgniter\HTTP\CURLRequest;
use Config\Services;

class JSSDK
{
    protected string $appId;
    protected string $appSecret;
    protected bool   $debug;
    protected $cache;

    public function __construct()
    {
        // Pull from .env instead of CI3 constants
        $this->appId     = env('WECHAT_APP_ID');
        $this->appSecret = env('WECHAT_APP_SECRET');
        $this->debug     = (bool) env('WECHAT_DEBUG', false);

        // CI4 cache service instead of $this->load->driver('cache')
        $this->cache = Services::cache();
    }

    public function getSignPackage(string $url): array
    {
        $jsapiTicket = $this->getJsApiTicket();
        $timestamp   = time();
        $nonceStr    = $this->createNonceStr();

        $rawString = "jsapi_ticket={$jsapiTicket}"
                   . "&noncestr={$nonceStr}"
                   . "&timestamp={$timestamp}"
                   . "&url={$url}";

        $signature = sha1($rawString);

        return [
            'appId'     => $this->appId,
            'nonceStr'  => $nonceStr,
            'timestamp' => $timestamp,
            'url'       => $url,
            'signature' => $signature,
            'rawString' => $rawString,
            'debug'     => $this->debug,
        ];
    }

    protected function getJsApiTicket(): string
    {
        $cacheKey = 'wechat_jsapi_ticket_' . $this->appId;

        if ($ticket = $this->cache->get($cacheKey)) {
            return $ticket;
        }

        $accessToken = $this->getAccessToken();
        $url = "https://api.weixin.qq.com/cgi-bin/ticket/getticket"
             . "?type=jsapi&access_token={$accessToken}";

        $result = $this->httpGet($url);
        $ticket = $result['ticket'];

        $this->cache->save($cacheKey, $ticket, 7000);

        return $ticket;
    }

    protected function getAccessToken(): string
    {
        $cacheKey = 'wechat_access_token_' . $this->appId;

        if ($token = $this->cache->get($cacheKey)) {
            return $token;
        }

        $url = "https://api.weixin.qq.com/cgi-bin/token"
             . "?grant_type=client_credential"
             . "&appid={$this->appId}"
             . "&secret={$this->appSecret}";

        $result = $this->httpGet($url);
        $token  = $result['access_token'];

        $this->cache->save($cacheKey, $token, 7000);

        return $token;
    }

    protected function httpGet(string $url): array
    {
        $client   = Services::curlrequest();
        $response = $client->get($url);
        return json_decode($response->getBody(), true);
    }

    protected function createNonceStr(int $length = 16): string
    {
        $chars = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';
        $str   = '';
        for ($i = 0; $i < $length; $i++) {
            $str .= $chars[random_int(0, strlen($chars) - 1)];
        }
        return $str;
    }
}

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Step 2: Port Constants to .env

Old CI3 constants.php:

define('WECHAT_APP_ID',     'wx123456');
define('WECHAT_APP_SECRET', 'abc123');
define('WECHAT_DEBUG',      true);

New CI4 .env:

WECHAT_APP_ID     = wx123456
WECHAT_APP_SECRET = abc123
WECHAT_DEBUG      = true

Access anywhere via env('WECHAT_APP_ID').

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Step 3: Create a WeChatPlatform Shim (if needed)

<?php
// app/Libraries/WeChatPlatform.php

namespace App\Libraries;

class WeChatPlatform
{
    protected JSSDK $jssdk;
    protected WeChatClient $client;

    public function __construct()
    {
        $this->jssdk   = new JSSDK();
        $this->client  = new WeChatClient();
    }

    public function getSignPackage(string $url): array
    {
        return $this->jssdk->getSignPackage($url);
    }

    // Proxy other methods as needed...
}

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Step 4: Fix Controllers (CI3 → CI4 Pattern)

CI3 (old):

class WeChatController extends CI_Controller {
    public function __construct() {
        parent::__construct();
        $this->load->library('JSSDK');
        $this->load->model('WeChatModel');
    }

    public function index() {
        $package = $this->jssdk->getSignPackage(current_url());
        $this->load->view('wechat/index', ['package' => $package]);
    }
}

CI4 (new):

<?php
// app/Controllers/WeChatController.php

namespace App\Controllers;

use App\Libraries\JSSDK;
use App\Models\WeChatModel;

class WeChatController extends BaseController
{
    protected JSSDK $jssdk;
    protected WeChatModel $wechatModel;

    public function __construct()
    {
        $this->jssdk        = new JSSDK();
        $this->wechatModel  = new WeChatModel();
    }

    public function index(): string
    {
        $package = $this->jssdk->getSignPackage(current_url());
        return view('wechat/index', ['package' => $package]);
    }
}

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Step 5: Enable Cache in CI4

In app/Config/Cache.php, set your preferred driver:

public string $handler = 'file'; // or 'redis', 'memcached'

For Redis:

# .env
cache.handler = redis
cache.redis.host = 127.0.0.1
cache.redis.port = 6379

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Step 6: Verify Routes

In app/Config/Routes.php:

$routes->get('wechat',        'WeChatController::index');
$routes->post('wechat/oauth', 'WeChatController::oauth');

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Migration Checklist

Task	Status
WeChatClient.php rewritten	✅ Done
JSSDK.php rewritten	🔧 Use code above
WeChatPlatform shim	🔧 Use code above
Constants → .env	🔧 Add entries
Controllers fixed	🔧 Per-controller fix
Cache configured	🔧 Check Config/Cache.php
Routes verified	🔧 Check Config/Routes.php

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Key CI3 → CI4 Mapping Summary

CI3	CI4
get_instance()	Constructor injection
$this->load->library('X')	new X() or Services::X()
$this->load->model('X')	new X() (extends Model)
$this->load->view()	return view()
$this->load->driver('cache')	Services::cache()
define('CONST', val)	env('CONST') in .env
$this->input->get()	$this->request->getGet()

Work through each file top-to-bottom using the pattern table above and the app will come back to life.

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