title: Substitute for apc_exists()
body: <p>I want to replace <code>Apc_bc</code> to <code>APCU</code>.</p>
  
  <p>What I use <code>Apc_bc</code> now are just three function.</p>
  
  <p><code>apc_exists()</code></p>
  
  <p><code>apc_fetch()</code></p>
  
  <p><code>apc_store()</code></p>
  
  <p>then, now I found <code>apcu_fetch()</code> and <code>apc_store()</code>.</p>
  
  <p>However I can't find the substitute for <code>apc_exists()</code>.</p>
  
  <p>How can I solve it ??</p>
  
  <p><code>Environment - PHP7.3.8</code></p>