folderweb/app/cache.php

<?php

function buildCacheKey(string $filePath, string $langPrefix = ''): string {
    $mtime = filemtime($filePath);

    // Include metadata.ini mtime so metadata edits invalidate cache
    $metadataFile = dirname($filePath) . '/metadata.ini';
    $metaMtime = file_exists($metadataFile) ? filemtime($metadataFile) : 0;

    // Include global config mtime so config changes invalidate cache
    $customConfig = __DIR__ . '/../custom/config.ini';
    $defaultConfig = __DIR__ . '/default/config.ini';
    $configMtime = file_exists($customConfig) ? filemtime($customConfig) : filemtime($defaultConfig);

    return md5($filePath . $mtime . $metaMtime . $configMtime . $langPrefix);
}

function getCachedMarkdown(string $filePath, string $langPrefix = ''): ?string {
    $cacheDir = '/tmp/folderweb_cache';
    $cachePath = "$cacheDir/" . buildCacheKey($filePath, $langPrefix);

    if (file_exists($cachePath)) {
        return file_get_contents($cachePath);
    }

    return null;
}

function setCachedMarkdown(string $filePath, string $html, string $langPrefix = ''): void {
    $cacheDir = '/tmp/folderweb_cache';
    if (!is_dir($cacheDir)) {
        mkdir($cacheDir, 0755, true);
    }

    $cachePath = "$cacheDir/" . buildCacheKey($filePath, $langPrefix);

    file_put_contents($cachePath, $html);
}