微信公眾號開發入門：接口驗證、訊息接收與回覆（文字/圖文）完整實作

成為微信公眾號開發者的第一步是通過接口驗證。本文提供完整的微信基礎類（Weixin）、接口處理腳本（weixin.php）、驗證測試腳本，涵蓋文字訊息、圖文訊息回覆，並說明驗證流程與部署要點。

核心類：Weixin.class.php

<?php
class Weixin {
    public $token = '';
    public $debug = false;
    public $setFlag = false;
    public $msgtype = 'text';
    public $msg = [];

    public function __construct($token, $debug) {
        $this->token = $token;
        $this->debug = $debug;
    }

    // 取得使用者訊息
    public function getMsg() {
        $postStr = $GLOBALS['HTTP_RAW_POST_DATA'];
        if ($this->debug) $this->write_log($postStr);
        if (!empty($postStr)) {
            $this->msg = (array)simplexml_load_string($postStr, 'SimpleXMLElement', LIBXML_NOCDATA);
            $this->msgtype = strtolower($this->msg['MsgType']);
        }
    }

    // 回覆文字訊息
    public function makeText($text = '') {
        $tpl = "<xml>
<ToUserName><![CDATA[{$this->msg['FromUserName']}]]></ToUserName>
<FromUserName><![CDATA[{$this->msg['ToUserName']}]]></FromUserName>
<CreateTime>%s</CreateTime>
<MsgType><![CDATA[text]]></MsgType>
<Content><![CDATA[%s]]></Content>
<FuncFlag>%s</FuncFlag>
</xml>";
        return sprintf($tpl, time(), $text, $this->setFlag ? 1 : 0);
    }

    // 回覆圖文訊息
    public function makeNews($newsData = []) {
        $itemTpl = "<item>
<Title><![CDATA[%s]]></Title>
<Description><![CDATA[%s]]></Description>
<PicUrl><![CDATA[%s]]></PicUrl>
<Url><![CDATA[%s]]></Url>
</item>";
        $items = '';
        $count = min(count($newsData), 10); // 最多 10 條
        for ($i = 0; $i < $count; $i++) {
            $item = $newsData[$i];
            $items .= sprintf($itemTpl, $item['Title'], $item['Description'], $item['PicUrl'], $item['Url']);
        }
        $tpl = "<xml>
<ToUserName><![CDATA[{$this->msg['FromUserName']}]]></ToUserName>
<FromUserName><![CDATA[{$this->msg['ToUserName']}]]></FromUserName>
<CreateTime>%s</CreateTime>
<MsgType><![CDATA[news]]></MsgType>
<ArticleCount>$count</ArticleCount>
<Articles>$items</Articles>
<FuncFlag>%s</FuncFlag>
</xml>";
        return sprintf($tpl, time(), $this->setFlag ? 1 : 0);
    }

    public function reply($data) {
        if ($this->debug) $this->write_log($data);
        echo $data;
    }

    // 接口驗證
    public function valid() {
        if ($this->checkSignature()) {
            echo $_GET['echostr'];
            exit;
        } else {
            $this->write_log('驗證失敗');
            exit;
        }
    }

    private function checkSignature() {
        $signature = $_GET['signature'];
        $timestamp = $_GET['timestamp'];
        $nonce     = $_GET['nonce'];
        $tmpArr = [$this->token, $timestamp, $nonce];
        sort($tmpArr, SORT_STRING);
        $tmpStr = sha1(implode($tmpArr));
        return $tmpStr === $signature;
    }

    private function write_log($log) {
        // 實作寫入日誌檔案或資料庫
        error_log(date('Y-m-d H:i:s') . " $log\n", 3, __DIR__ . '/weixin.log');
    }
}
?>

接口處理腳本：weixin.php

<?php
header('Content-Type: text/html; charset=utf-8');
require_once 'Weixin.class.php';

define('TOKEN', 'your_token_here');
define('DEBUG', false);

$weixin = new Weixin(TOKEN, DEBUG);
// $weixin->valid(); // 驗證通過後註解掉

$weixin->getMsg();
$type = $weixin->msgtype;
$from = $weixin->msg['FromUserName'];

if ($type === 'text') {
    $content = $weixin->msg['Content'];
    if ($content === '你好') {
        $reply = $weixin->makeText('歡迎關注！');
    } else {
        // 示例：回覆圖文
        $articles = [
            ['Title'=>'電腦學習網', 'Description'=>'十萬個為什麼', 'PicUrl'=>'https://example.com/img1.jpg', 'Url'=>'https://www.why100000.com/'],
            ['Title'=>'PHP學習網', 'Description'=>'大型PHP社區', 'PicUrl'=>'https://example.com/img2.jpg', 'Url'=>'https://www.veryphp.cn/'],
        ];
        $reply = $weixin->makeNews($articles);
    }
} elseif ($type === 'event' && $weixin->msg['Event'] === 'subscribe') {
    $reply = $weixin->makeText('感謝關注，輸入「你好」體驗功能。');
} else {
    $reply = $weixin->makeText('收到：' . $content);
}

$weixin->reply($reply);
?>

驗證測試腳本（cURL 模擬）

<?php
define('TOKEN', 'your_token_here');
$echostr = 'test_echostr';
$timestamp = (string)time();
$nonce = 'test_nonce';

$tmpArr = [TOKEN, $timestamp, $nonce];
sort($tmpArr, SORT_STRING);
$signature = sha1(implode($tmpArr));

$url = 'https://yourdomain.com/weixin.php';
$params = http_build_query([
    'signature' => $signature,
    'timestamp' => $timestamp,
    'nonce' => $nonce,
    'echostr' => $echostr
]);

$ch = curl_init("$url?$params");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$result = curl_exec($ch);
curl_close($ch);
echo "驗證回傳: $result"; // 應輸出 test_echostr
?>

部署檢查清單

進階擴充方向

• 接入資料庫實現關鍵字自動回覆、客服系統
• 實現自訂選單（菜單）與網頁授權登入
• 使用 EasyWeChat 等成熟 SDK 替代手工類別
• 加入訊息加密模式（安全模式/相容模式）