PHP apcu_cache_info() Function: Usage and Examples

Reports APCu shared cache statistics and optionally entry listings.

What It Does and When to Use It

Inspect global statistics without dumping every cache key. 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 in CLI may be disabled and is process-group/local-host cache, not a shared distributed cache.

Example 1: Basic Operation

Inspect global statistics without dumping every cache key.

<?php
if (function_exists('apcu_cache_info') && filter_var(ini_get('apc.enabled'), FILTER_VALIDATE_BOOL)) {
     $info = apcu_cache_info(true);
     echo 'Hits: ', $info['num_hits'] ?? 0;
 }

Example 2: Behavior and Validation

Calculate hit rate with safe handling for an empty cache.

<?php
$stats = apcu_cache_info(true);
 $hits = (int)($stats['num_hits'] ?? 0);
 $misses = (int)($stats['num_misses'] ?? 0);
 echo $hits + $misses ? round($hits / ($hits + $misses) * 100, 1) . '%' : 'No traffic';

Practical Example: Application Use

Review cache pressure and evictions; keys are sensitive in production.

<?php
$details = apcu_cache_info(false);
 foreach (['num_entries', 'mem_size', 'expunges'] as $key) {
     echo $key, ': ', $details[$key] ?? 'not available', "
";
 }

Important Behavior and Edge Cases

The second example highlights: Calculate hit rate with safe handling for an empty cache. The practical example adds: Review cache pressure and evictions; keys are sensitive in production.

Comparison with Related Approaches

Common Beginner Mistakes

Key Takeaways

• Reports APCu shared cache statistics and optionally entry listings.
• Review cache pressure and evictions; keys are sensitive in production.
• Define TTL, invalidation, and concurrency behavior separately from the cache storage API.