PHP中如何有效处理token的缓存问题以减少API请求次数？

<?php
header("Content-type:text/html;charset=utf-8");
$cacheFile = __DIR__ . '/access_token.cache'; // 缓存文件路径

function getAccessToken($appId, $appSecret) {
    $tokenUrl = "https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid={$appId}&secret={$appSecret}";
    $ch = curl_init();
    curl_setopt_array($ch, [
        CURLOPT_URL => $tokenUrl,
        CURLOPT_SSL_VERIFYPEER => false,
        CURLOPT_SSL_VERIFYHOST => false,
        CURLOPT_RETURNTRANSFER => true,
    ]);
    $response = curl_exec($ch);
    curl_close($ch);
    $data = json_decode($response, true);
    if (isset($data['access_token'])) {
        return $data;
    } else {
        return false; // 获取Token失败
    }
}

function cacheAccessToken($accessToken, $expireTime) {
    global $cacheFile;
    $data = "{$expireTime} {$accessToken}";
    if (!file_exists($cacheFile)) {
        touch($cacheFile);
    }
    if (flock($cacheFile, LOCK_EX)) { // 获取独占锁
        file_put_contents($cacheFile, $data);
        flock($cacheFile, LOCK_UN); // 释放锁
    }
}

function getCachedAccessToken() {
    global $cacheFile;
    if (file_exists($cacheFile)) {
        if (flock($cacheFile, LOCK_SH)) { // 获取共享锁
            $data = file_get_contents($cacheFile);
            flock($cacheFile, LOCK_UN); // 释放锁
            list($cacheTime, $accessToken) = explode(' ', $data, 2);
            if (time() < $cacheTime) {
                return $accessToken;
            }
        }
    }
    return false;
}

// ... (其余代码保持不变，仅修改Token获取和使用部分) ...

$accessToken = getCachedAccessToken();
if (!$accessToken) {
    $appId = 'xxx';
    $appSecret = 'xxx';
    $tokenData = getAccessToken($appId, $appSecret);
    if ($tokenData) {
        $accessToken = $tokenData['access_token'];
        $expireTime = time() + $tokenData['expires_in'] - 600; // 预留600秒缓冲
        cacheAccessToken($accessToken, $expireTime);
    } else {
        // 处理获取Token失败的情况
        die("获取access_token失败");
    }
}

$url = "https://api.weixin.qq.com/cgi-bin/message/template/send?access_token=" . $accessToken;
// ... (发送消息的代码保持不变) ...