Using APCu for Application-Level Caching

APCu stores application data in shared memory on a single PHP host, separate from OPcache.

What It Does and When to Use It

Store one small application value with an explicit TTL. APCu stores local application data, Redis is external and can be shared among hosts, and OPcache stores compiled code.

Requirements, Inputs and Expected Behavior

Confirm the runtime, extension, environment variables, and permissions before running the examples in production. APCu cache contents are not shared across servers and disappear on restart.

Example 1: Basic Operation

Store one small application value with an explicit TTL.

<?php
if (!function_exists('apcu_enabled') || !apcu_enabled()) throw new RuntimeException('APCu is disabled');
apcu_store('greeting:v1','Hello',60);
echo apcu_fetch('greeting:v1');

Example 2: Behavior and Validation

Use the success output parameter because false can be a valid cached value.

<?php
$success=false;
$value=apcu_fetch('feature:maintenance',$success);
echo $success?'Key found':'Cache miss';

Practical Example: Application Use

Populate cache on miss with apcu_entry when a single-host APCu cache is appropriate.

<?php
$key='policy:revision:4';
$policy=apcu_entry($key,static fn()=>['max_items'=>20],120);
echo (int)$policy['max_items'];

Important Behavior and Edge Cases

The second example highlights: Use the success output parameter because false can be a valid cached value. The practical example adds: Populate cache on miss with apcu_entry when a single-host APCu cache is appropriate.

Comparison with Related Approaches

Common Beginner Mistakes

Key Takeaways

• APCu stores application data in shared memory on a single PHP host, separate from OPcache.
• Populate cache on miss with apcu_entry when a single-host APCu cache is appropriate.
• Define TTL, invalidation, and concurrency behavior separately from the cache storage API.