APC vs Memcached: The Best PHP Cache for WordPress

When it comes to optimizing WordPress performance, caching is one of the most powerful tools at your disposal. With PHP handling most of the heavy lifting in WordPress, implementing a solid caching strategy can dramatically speed up your site. But with so many caching options available, it can be challenging to determine which one is best for your setup. Two popular choices for PHP caching are APC (Alternative PHP Cache) and Memcached.

What is APC?

APC (Alternative PHP Cache) is a robust solution that provides opcode caching for PHP. Opcode caching works by storing precompiled script bytecode in memory, reducing the need for PHP to load and parse scripts on each request. This dramatically improves PHP performance by cutting down the processing time for repetitive operations.

Key Benefits of APC:

• Opcode Caching: APC stores the compiled PHP code, so your server doesn’t need to recompile it for every request.
• User Data Caching: APC also allows caching of user data, which can further reduce database queries and speed up your WordPress site.
• Simple Integration: APC is relatively straightforward to install and configure, making it accessible even for those with limited server experience.

What is Memcached?

Memcached is a distributed memory object caching system, widely recognized for its ability to handle large caches spread across multiple servers. Unlike APC, which focuses primarily on opcode caching, Memcached excels in caching database query results and objects, making it a powerhouse for dynamic WordPress sites with heavy traffic.

Key Benefits of Memcached:

• Distributed Caching: Memcached can be set up on multiple servers, allowing for greater scalability and reliability in large environments.
• Efficient Data Storage: It stores data in memory, which provides ultra-fast access to cached data, reducing load on the database.
• Versatile Caching: Memcached is particularly effective at caching complex query results and objects, making it ideal for data-heavy applications.

APC vs. Memcached: A Comparative Analysis

1. Speed and Performance

• APC: By caching the compiled PHP code, APC significantly reduces the overhead of PHP execution. This results in faster page loads, especially for PHP-intensive WordPress sites.
• Memcached: While not focused on opcode caching, Memcached can speed up database-driven applications by reducing the need for repeated database queries. This is particularly beneficial for sites with high traffic and complex queries.

1. Scalability

• APC: Best suited for single-server environments, APC’s opcode caching can only be utilized on the server it’s installed on. While this works well for small to medium-sized sites, it may not be ideal for large-scale applications.
• Memcached: Designed for distributed environments, Memcached can scale across multiple servers. This makes it the go-to solution for large sites or those expecting significant growth.

1. Ease of Use

• APC: Installation and configuration are relatively straightforward. For those running PHP 5.4 or earlier, APC can be easily integrated, though it’s important to note that APC is no longer updated, with APCu serving as its modern replacement for user data caching.
• Memcached: While slightly more complex to set up, Memcached’s configuration is manageable for most developers. Its flexibility in handling large caches makes it worth the extra effort for larger sites.

1. Compatibility

• APC: Best suited for PHP 5.4 and earlier. If you’re running PHP 7 or later, APCu is recommended for user data caching, as full APC support is no longer available.
• Memcached: Compatible with a wide range of PHP versions, including the latest releases, Memcached integrates seamlessly with WordPress through popular plugins like W3 Total Cache or WP Rocket.

Which One Should You Choose?

The decision between APC and Memcached ultimately depends on your specific needs:

• Choose APC if: You’re running a single-server environment with PHP 5.4 or earlier and want a straightforward, powerful opcode caching solution. For modern environments, consider APCu in combination with an opcode cache like Zend OPcache.
• Choose Memcached if: You’re managing a large or distributed site with heavy database queries and need a caching system that can scale efficiently across multiple servers. Memcached is the ideal choice for high-traffic sites looking to minimize database load and enhance performance.

Conclusion

Both APC and Memcached offer significant performance benefits for WordPress sites, but their strengths lie in different areas. APC is ideal for those seeking fast and efficient opcode caching on a single server, while Memcached shines in large-scale, database-driven environments.