How to Combine apcu_fetch and apcu_exists for Cache Preloading

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<p>/**</p>
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<p>How to Combine apcu_fetch and apcu_exists for Cache Preloading</p>
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<p>Using APCu (Alternative PHP Cache User) in PHP can greatly improve application performance,</p>
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<p>especially for frequently accessed data, such as configuration files or popular query results.</p>
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<p>To optimize cache hit rates, you can combine apcu_exists and apcu_fetch to implement cache preloading.</p>
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<p>Understanding apcu_exists and apcu_fetch</p>
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<p>apcu_exists($key): Checks whether a specific key exists in the cache.</p>
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<p>apcu_fetch($key, &$success): Attempts to fetch the value for a key from the cache. Returns the value if it exists, otherwise returns false. The $success parameter is set to true or false.</p>
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<p>Cache Preloading Concept</p>
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<p>The main goal of cache preloading is to generate and store data in the cache ahead of time if it doesn’t exist,</p>
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<p>avoiding recalculations or database queries on every request.</p>
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<p>Typical workflow:</p>
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<p>a. Check if the cache exists:</p>
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<p>Use apcu_exists($key). If it returns false, the cache is missing and preloading is needed.</p>
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<p>b. Preload data:</p>
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<p>Fetch data from the database or other sources based on business logic.</p>
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<p>c. Store in cache:</p>
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<p>Use apcu_store($key, $value, $ttl) to save the data in cache, where $ttl is the cache lifetime.</p>
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<p>d. Retrieve from cache:</p>
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<p>Use apcu_fetch($key) to read the cache, ensuring that even if one concurrent request writes the cache first,</p>
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<p>subsequent requests can fetch it directly.</p>
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<p>Example Code<br>
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<p>$cacheKey = 'user_config';<br>
$cacheTTL = 3600; </span>// Cache for 1 hour</p>
<p>// Check if cache exists<br>
if (!apcu_exists($cacheKey)) {<br>
// Preload data, e.g., fetch from database<br>
$data = [<br>
'theme' => 'dark',<br>
'language' => 'zh-CN',<br>
'items_per_page' => 20<br>
];<br>
// Store in cache<br>
apcu_store($cacheKey, </span>$data, </span>$cacheTTL);<br>
}</p>
<p>// Retrieve data from cache<br>
$data = apcu_fetch($cacheKey, </span>$success);<br>
if ($success) {<br>
echo "Cache loaded successfully: ";<br>
print_r($data);<br>
} else {<br>
echo "Failed to retrieve cache, data needs to be regenerated";<br>
}</p>
<p>/**</p>
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<p>4. Notes</p>
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<p>To avoid regenerating cache under high concurrency, use locking mechanisms or check-and-set solutions.</p>
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<p>Periodically clean up expired cache to prevent excessive memory usage.</p>
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<p>apcu_exists and apcu_fetch can be used together, or you can use apcu_fetch directly and check the returned $success to determine existence, reducing one cache access.</p>
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<p>Summary:</p>
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<p>Combining apcu_exists and apcu_fetch effectively implements cache preloading and improves PHP application performance. Key steps:</p>
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<p>Check if cache exists</p>
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<p>Generate and store data if missing</p>
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<p>Use apcu_fetch to retrieve cache content<br>
*/</p>
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