Zend OpCache vs. Alternative PHP Cache (APC): Which is Best for WordPress

When it comes to WordPress performance, caching is crucial. Two of the most popular PHP caching options are Zend OpCache and Alternative PHP Cache (APC). Both tools aim to speed up your WordPress site by storing precompiled script bytecode in memory, reducing the load time of your site by eliminating the need to compile PHP code on every request.

What are the differences between Zend OpCache and APC, and which is better for WordPress?

What is Zend OpCache?

Zend OpCache is a caching engine built into PHP that improves PHP performance by storing precompiled script bytecode in shared memory. This eliminates the need for PHP to load and parse scripts on each request. As part of PHP’s core, Zend OpCache is highly optimized for compatibility and performance, making it a reliable choice for any PHP-based application, including WordPress.

Key Features of Zend OpCache:

• Reduced CPU Usage: Caching precompiled bytecode Zend OpCache significantly reduces the server’s CPU usage and faster execution of PHP scripts.
• Built-in PHP Extension: Zend OpCache is included in PHP 5.5 and later, meaning you don’t need to install additional modules. It’s easy to activate and configure.
• Memory Efficiency: Zend OpCache allows you to control the amount of memory allocated for cache storage, optimizing how much of your server’s RAM is used.

What is APC (Alternative PHP Cache)?

APC, or Alternative PHP Cache, is another caching engine designed to improve the performance of PHP applications by caching bytecode. Unlike Zend OpCache, APC also offers data caching, allowing you to store user data in a shared memory space. However, APC is no longer actively maintained as a core PHP extension since PHP 5.5, it was largly replaced by Zend OpCache.

Key Features of APC:

• Bytecode Caching: Like Zend OpCache, APC speeds up PHP execution by caching precompiled bytecode, reducing the need to compile code on each request.
• Data Caching: APC allows for data caching, enabling you to store and retrieve user-specific data in memory, which can be useful for optimizing session management or storing frequently accessed data.
• Legacy Support: APC is still used in older PHP versions (pre-5.5) but is not recommended for new projects due to lack of ongoing support.

Zend OpCache vs. APC: Key Differences

1. Performance and Efficiency:
   • Zend OpCache: Designed to be faster and more efficient, Zend OpCache is tightly integrated with PHP’s core, leading to better overall performance. It is specifically optimized for modern PHP environments and is a preferred choice for most PHP-based applications, including WordPress.
   • APC: While still effective, APC is not as optimized as Zend OpCache, particularly in the latest PHP versions. It also uses more server resources for data caching, which can impact performance on resource-constrained servers.
2. Ease of Use:
   • Zend OpCache: Since it is built into PHP, Zend OpCache is straightforward to activate. Most hosting providers automatically enable it for PHP 5.5 and later, making it a hassle-free option.
   • APC: Requires manual installation and configuration, especially for PHP versions 5.4 and below. For users running older PHP versions, this can be more complex and time-consuming.
3. Compatibility:
   • Zend OpCache: As part of PHP’s core since version 5.5, Zend OpCache is compatible with all modern PHP applications. It receives regular updates and improvements with each new PHP release.
   • APC: Since APC is no longer maintained, it may not be compatible with the latest PHP versions or WordPress plugins. This can lead to potential compatibility issues, especially if you’re running a modern WordPress setup.
4. Data Caching:
   • Zend OpCache: Focuses solely on bytecode caching and does not provide a data caching mechanism.
   • APC: Offers both bytecode and data caching, which can be useful in specific scenarios, though the need for data caching can often be fulfilled by other more modern tools like Redis or Memcached.

Which is Recommended for WordPress?

Given the differences, Zend OpCache is the clear choice for WordPress users. Here’s why:

• Performance: Zend OpCache delivers faster and more efficient PHP execution, which is critical for a dynamic platform like WordPress. It reduces CPU usage and improves the overall speed of your site.
• Ease of Use: Most WordPress hosting providers enable Zend OpCache by default, so you can take advantage of its benefits with minimal setup.
• Compatibility: As part of PHP’s core, Zend OpCache is fully compatible with all modern PHP versions and WordPress setups. It receives regular updates and improvements, ensuring optimal performance over time.

APC, while once a powerful tool, is now outdated and not recommended for new projects. If you’re running an older PHP version and need data caching, consider upgrading to a more recent PHP version and using Zend OpCache in combination with a dedicated data caching solution like Redis or Memcached.

Turn on APCu and Opcache in W3 Cache Plugin

Conclusion: Zend OpCache is the Future

APC played a significant role in PHP optimization in the past, Zend OpCache is now the better and more future-proof solution, especially for WordPress.

FAQs:

1. Can I use both Zend OpCache and APC together? No, it’s not recommended to use both together. Zend OpCache is designed to replace APC’s bytecode caching functionality in PHP 5.5 and later. Using both could lead to conflicts and performance issues.

2. Do I need a plugin to enable Zend OpCache on my WordPress site?No, you do not need a plugin. Zend OpCache is a PHP extension, and most modern hosting providers enable it by default.

3. How do I know if Zend OpCache is working? You can verify Zend OpCache is working by creating a PHP info file on your server. Look for the “Zend OPcache” section, which will show you the current status and configuration. Alternatively, install w3 cache plugin Setting > Object Cache Dropdown.