Using caching is one of the most effective ways to improve the performance of PHP applications, which reduces server load and speeds up response time by avoiding duplicate and expensive operations. 1. Enable OPcache for opcode caching, store precompiled script bytecode in memory, set opcache.enable to On, and enable CLI cache and adjust memory consumption as needed; 2. Cache database query results, use tools such as APCu, Memcached or Redis to temporarily store infrequently, and set appropriate TTL according to the data update frequency; 3. Implement page or fragment cache, store static HTML content and quickly return based on unique keys to reduce duplicate processing; 4. Use HTTP cache headers such as Cache-Control and Last-Modified to allow the browser and proxy to cache responses, further reducing server requests. A rational choice of cache strategies can significantly optimize application performance.

Caching is one of the most effective ways to boost performance in PHP applications. It reduces server load, speeds up response times, and improves user experience by avoiding repeated expensive operations like database queries or complex computings.

Use Opcode Caching with OPcache

PHP scripts are compiled into opcode every time they're executed—this adds overhead. OPcache stores precompiled script bytecode in memory so it doesn't need to be reloaded and re-parsed on each request.

• Make sure opcache.enable is set to On in your php.ini .
• Enable opcache.enable_cli if you want caching for CLI scripts too.
• Adjust opcache.memory_consumption depending on your app size (default is 128MB, but larger apps may need more).
• Consider setting opcache.validate_timestamps to Off in production (just remember to manually reset the cache when code changes).

This is usually already included in most modern PHP versions (5.5 ) and is easy to enable—don't skip it.

Cache Database Queries and Results

Repeatedly fetching the same data from a database can slow things down fast. If certain queries don't change often, store their results temporarily using a caching layer.

You can use:

• APCu – A simple in-memory key-value store for PHP.
• Memcached or Redis – More scalable options that work across multiple servers.

For example:

 $data = apcu_fetch('user_profile_123');
if ($data === false) {
    $data = fetchFromDatabase(); // Your DB query function
    apcu_store('user_profile_123', $data, 3600); // Cache for 1 hour
}

Choose an expiration time based on how fresh the data needs to be. For frequently updated data, keep TTL (Time To Live) low; for static content, go higher.

Implement Page or Fragment Caching

If whole pages or parts of them don't change often, caching the HTML output can save a lot of processing.

• Store generated HTML files or fragments on disk or in memory.
• Use a unique key per URL or user context (like language or logged-in status).
• Set up a check early in your request lifecycle to serve cached content before doing any real processing.

For instance:

 $cacheKey = md5($_SERVER['REQUEST_URI']);
$cached = getFromCache($cacheKey);
if ($cached) {
    echo $cached;
    exit;
}

// Otherwise generate page content...

saveToCache($cacheKey, $content);

Make sure to bypass or refresh the cache appropriately when content changes—otherwise users might see outdated info.

Use HTTP Caching Headers

Browsers and proxies can also cache responses if you tell them to. This helps reduce requests hitting your server at all.

Use headers like:

• Cache-Control : Tells browsers and intermediaries how long to cache.
• ETag or Last-Modified : Let clients know if the content has changed since last request.

Example:

 header('Cache-Control: public, max-age=86400'); // 24 hours
header('Last-Modified: ' . gmdate('D, d MYH:i:s', filemtime('content.txt')) . ' GMT');

If the browser sees that nothing changed, it'll just load from its own cache—no round trip needed.

That's the basic idea. You don't have to do all of these at once, but even implementing one or two can make a noticeable difference. The trick is knowing which parts of your app benefit most from caching—and not over-caching things that change too often.

The above is the detailed content of How do I use caching to improve the performance of PHP applications?. For more information, please follow other related articles on the PHP Chinese website!