Are there any potential pitfalls or drawbacks to caching variables in PHP?

One potential pitfall of caching variables in PHP is that it can lead to stale data if the cached value is not updated frequently. To avoid this issue, it is important to implement a mechanism to refresh the cached value periodically or when the underlying data changes. 

// Example of caching a variable with automatic refresh
function get_cached_data() {
    $cache_key = 'cached_data';
    $cached_data = apc_fetch($cache_key);
    
    if (!$cached_data) {
        // Fetch data from database or API
        $data = fetch_data_from_source();
        
        // Cache the data with a TTL of 1 hour
        apc_store($cache_key, $data, 3600);
        
        return $data;
    } else {
        // Check if it's time to refresh the cache
        $last_updated = apc_fetch($cache_key . '_last_updated');
        if (time() - $last_updated > 3600) {
            // Refresh the cached data
            $data = fetch_data_from_source();
            apc_store($cache_key, $data, 3600);
            apc_store($cache_key . '_last_updated', time());
        }
        
        return $cached_data;
    }
}

Keywords

caching variables PHP drawbacks performance

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