Cross‑Platform PHP Caching: File and Redis Strategies with Code Samples

In PHP development, caching is essential for improving performance and response speed, and ensuring compatibility across different platforms is a key concern. The article presents two common caching approaches—file caching and Redis caching—along with complete code examples for each.

File Cache

File caching works on any platform. The following code demonstrates how to store and retrieve cached data using the filesystem, checking for existence and expiration (1 hour) before falling back to a data source.

<?php
function getCache($key) {
    $cacheDir = '/tmp/cache/'; // cache directory
    $filename = $cacheDir . md5($key) . '.txt'; // generate cache filename

    if (file_exists($filename) && (time() - filemtime($filename) < 3600)) {
        // Return cached data if file exists and is not expired
        return file_get_contents($filename);
    } else {
        // Retrieve data from database or other source
        $data = fetchDataFromDatabase($key);
        // Store data in cache file
        file_put_contents($filename, $data);
        return $data;
    }
}

function fetchDataFromDatabase($key) {
    // Logic to query database or other data source
    // ...
}
?>

The code uses file_exists() to verify the cache file, filemtime() to check its age, file_get_contents() to read cached data, and file_put_contents() to write new data.

Redis Cache

Redis provides a fast, efficient caching solution. The example below shows how to connect to a Redis server, check for an existing, unexpired key, retrieve cached data, or fall back to a data source and store the result in Redis with an expiration time.

<?php
function getCache($key) {
    $redis = new Redis();
    if ($redis->connect('127.0.0.1', 6379)) {
        // Connection successful
        if ($redis->exists($key) && $redis->ttl($key) > 0) {
            // Return cached data if it exists and is not expired
            return $redis->get($key);
        } else {
            // Retrieve data from database or other source
            $data = fetchDataFromDatabase($key);
            // Store data in Redis cache
            $redis->set($key, $data);
            $redis->expire($key, 3600);
            return $data;
        }
    } else {
        // Fallback to file cache if Redis connection fails
        return getCacheFromFile($key);
    }
}

function fetchDataFromDatabase($key) {
    // Logic to query database or other data source
    // ...
}

function getCacheFromFile($key) {
    // Use file cache as a backup strategy
    // ...
}
?>

This snippet uses the Redis extension to create a Redis instance, connect() to the server, exists() and ttl() to verify cache validity, get() to read cached data, set() to store data, and expire() to set the expiration time.

Overall, when using caching in PHP, developers should consider platform compatibility and choose the appropriate strategy—file or Redis—based on the deployment environment to achieve efficient caching, improved system performance, and better user experience.