Polyfill Apcu Laravel Package

Getting Started

Install via Composer: composer require symfony/polyfill-apcu. No configuration needed—it auto-registers fallbacks for apcu_* functions when the APCu extension isn’t loaded (e.g., PHP < 5.5, shared hosting, Docker containers without extension). If your app already uses functions like apcu_store() or apcu_fetch(), they’ll work out-of-the-box on environments lacking the native extension. Start by verifying your code already relies on APCu; this polyfill doesn’t add new functionality—it only ensures existing APCu calls succeed.

Implementation Patterns

• Reusable packages: Declare as a suggested dependency in composer.json ("suggest": {"symfony/polyfill-apcu": "..."}) so consumers can opt-in—avoid forcing installation on environments where APCu is guaranteed (e.g., modern Laravel apps with ext-apcu).
• Laravel cache drivers: Use in custom cache drivers (e.g., ApcuStore) that fall back to APCu functions internally. Laravel’s Cache::driver('apcu') won’t auto-fallback, but your custom implementation can leverage this polyfill seamlessly.
• Testing environments: Configure CI (e.g., GitHub Actions, local Docker) with PHP images without ext-apcu to validate compatibility. The polyfill ensures tests relying on APCu functions pass without mocking or environment-specific branching.
• Legacy migration: When upgrading apps from PHP 5.x to 7.x/8.x on mixed infrastructure, keep this as a transitional dependency until all targets support the native extension.

Gotchas and Tips

• Extension precedence: PHP always prefers native extensions over polyfills—even if apc.enabled=0, the extension’s stub functions are loaded, and the polyfill won’t activate. Confirm via php -m | grep apcu; if present, the polyfill is ignored.
• Missing functions: Coverage is partial—older versions lack apcu_cas, apcu_inc, apcu_dec. Use function_exists('apcu_inc') before calling optional functions, or check source for exact API parity.
• Performance trade-offs: Pure-PHP fallbacks (typically array-backed) are 5–50× slower than native. Avoid高频 caching ops (e.g., per-request metadata dumps); prefer Redis/Memcached for performance-critical paths.
• Serialization differences: Uses PHP’s serialize(), which may alter object metadata (e.g., __wakeup() timing, static property loss). Test edge cases—especially if caching complex objects.
• Autoloading dependency: Only activates if included after Composer’s autoloader (via vendor/autoload.php). If manually loading files (e.g., custom bootstraps), ensure polyfill loads before any apcu_* calls.