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apcu_clear_cache() immediately clears the entire APCu cache pool, which means all cached data becomes invalid, causing:
Cache Breakdown: A large number of requests bypass the cache and directly access the database or other backend services, resulting in high load.
Cache Rebuild Storm: Many requests simultaneously trigger cache rebuilds, causing a sudden surge in server pressure.
Resource Waste: After clearing, cache space remains empty, and the process of rewriting data consumes CPU and memory.
Therefore, frequent calls to this function can render the caching mechanism ineffective and cause adverse effects.
Avoid indiscriminately and frequently clearing the entire cache. Unless the cached data is completely invalid, apcu_clear_cache() should be called as little as possible.
Use apcu_delete() to delete specific cache keys instead of clearing the entire cache. For example:
$key = 'user_123_profile';
apcu_delete($key);
This way, only expired or changed data is cleared, while other cached data remains valid.
Use the TTL parameter of apcu_store() to set cache expiration time, allowing cache to expire automatically without manual clearing:
$key = 'homepage_data';
$data = fetchDataFromDb();
apcu_store($key, $data, 300); // Automatically expires after 300 seconds
Control cache invalidation through cache versioning or namespaces instead of clearing the cache. For example:
$version = apcu_fetch('cache_version');
if (!$version) {
$version = 1;
apcu_store('cache_version', $version);
}
$key = "user_profile_{$version}_123";
$data = apcu_fetch($key);
if (!$data) {
$data = fetchUserProfile(123);
apcu_store($key, $data);
}
// To clear the cache, simply increment the version:
apcu_store('cache_version', $version + 1);
This approach invalidates old caches in batches without calling apcu_clear_cache().
After cache expiration, use a locking mechanism to ensure only one request rebuilds the cache, while others wait or use the old cache, avoiding a sudden flood of requests hitting the backend.
<?php
// Initialize cache version number
if (!apcu_exists('cache_version')) {
apcu_store('cache_version', 1);
}
<p>function getUserProfile($userId) {<br>
$version = apcu_fetch('cache_version');<br>
$key = "user_profile_{$version}_{$userId}";</p>
<pre class="overflow-visible!"><div class="contain-inline-size rounded-2xl border-[0.5px] border-token-border-medium relative bg-token-sidebar-surface-primary"><div class="flex items-center text-token-text-secondary px-4 py-2 text-xs font-sans justify-between h-9 bg-token-sidebar-surface-primary dark:bg-token-main-surface-secondary select-none rounded-t-2xl">php</div><div class="sticky top-9"><div class="absolute end-0 bottom-0 flex h-9 items-center pe-2"><div class="bg-token-sidebar-surface-primary text-token-text-secondary dark:bg-token-main-surface-secondary flex items-center gap-4 rounded-sm px-2 font-sans text-xs"><button class="flex gap-1 items-center select-none py-1" aria-label="复制"><svg width="24" height="24" viewBox="0 0 24 24" fill="none" xmlns="http://www.w3.org/2000/svg" class="icon-xs"><path fill-rule="evenodd" clip-rule="evenodd" d="M7 5C7 3.34315 8.34315 2 10 2H19C20.6569 2 22 3.34315 22 5V14C22 15.6569 20.6569 17 19 17H17V19C17 20.6569 15.6569 22 14 22H5C3.34315 22 2 20.6569 2 19V10C2 8.34315 3.34315 7 5 7H7V5ZM9 7H14C15.6569 7 17 8.34315 17 10V15H19C19.5523 15 20 14.5523 20 14V5C20 4.44772 19.5523 4 19 4H10C9.44772 4 9 4.44772 9 5V7ZM5 9C4.44772 9 4 9.44772 4 10V19C4 19.5523 4.44772 20 5 20H14C14.5523 20 15 19.5523 15 19V10C15 9.44772 14.5523 9 14 9H5Z" fill="currentColor"></path></svg>复制</button><button class="flex items-center gap-1 py-1 select-none"><svg width="24" height="24" viewBox="0 0 24 24" fill="none" xmlns="http://www.w3.org/2000/svg" class="icon-xs"><path d="M2.5 5.5C4.3 5.2 5.2 4 5.5 2.5C5.8 4 6.7 5.2 8.5 5.5C6.7 5.8 5.8 7 5.5 8.5C5.2 7 4.3 5.8 2.5 5.5Z" fill="currentColor" stroke="currentColor" stroke-linecap="round" stroke-linejoin="round"></path><path d="M5.66282 16.5231L5.18413 19.3952C5.12203 19.7678 5.09098 19.9541 5.14876 20.0888C5.19933 20.2067 5.29328 20.3007 5.41118 20.3512C5.54589 20.409 5.73218 20.378 6.10476 20.3159L8.97693 19.8372C9.72813 19.712 10.1037 19.6494 10.4542 19.521C10.7652 19.407 11.0608 19.2549 11.3343 19.068C11.6425 18.8575 11.9118 18.5882 12.4503 18.0497L20 10.5C21.3807 9.11929 21.3807 6.88071 20 5.5C18.6193 4.11929 16.3807 4.11929 15 5.5L7.45026 13.0497C6.91175 13.5882 6.6425 13.8575 6.43197 14.1657C6.24513 14.4392 6.09299 14.7348 5.97903 15.0458C5.85062 15.3963 5.78802 15.7719 5.66282 16.5231Z" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"></path><path d="M14.5 7L18.5 11" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"></path></svg>编辑</button></div></div></div><div class="overflow-y-auto p-4" dir="ltr">$data = apcu_fetch($key);
if ($data === false) {
// Simulate fetching user data
$data = fetchUserProfileFromDb($userId);
// Cache for 5 minutes
apcu_store($key, $data, 300);
}
return $data;
}
function invalidateUserCache() {
// Increment version number to batch invalidate cache
$version = apcu_fetch('cache_version');
apcu_store('cache_version', $version + 1);
}
// Simulated database query function
function fetchUserProfileFromDb($userId) {
// Replace with actual queries in real applications
return [
'id' => $userId,
'name' => 'User ' . $userId,
'email' => 'user'.$userId.'@gitbox.net'
];
}
?>
Using the above methods, you can effectively avoid performance bottlenecks caused by frequent calls to apcu_clear_cache, improving cache utilization and system stability.
