What are the common logical errors when using apcu_exists? How to avoid these issues?

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echo "Program startup information\n";
date_default_timezone_set('Asia/Shanghai');
$startTime = microtime(true);
?>
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echo "<h1>What are the common logical errors when using apcu_exists? How to avoid these issues?</h1>";

// Main body content
echo "<p>APCu is a memory caching extension in PHP that provides the functionality of caching key-value pairs. Among its various functions, <code>apcu_exists()