title: Why won't composer use OPcache?
body: <p>I added </p>
  
  <pre><code>"require": {
      "ext-opcache": "*",
  </code></pre>
  
  <p>to <code>composer.json</code> for an eDirectory Symfony 2.8 app, but it gave me an error:</p>
  
  <pre><code>$ composer update
  Loading composer repositories with package information
  Updating dependencies (including require-dev)
  Your requirements could not be resolved to an installable set of packages.
  
    Problem 1
      - The requested PHP extension ext-opcache * is missing from your system. Install or enable PHP's opcache extension.
  </code></pre>
  
  <p>However, I <em>do</em> have OPcache installed!</p>
  
  <pre><code>$ php -r "phpinfo();" | grep OPcache -a3
  Zend OPcache
  
  Opcode Caching =&gt; Up and Running
  Optimization =&gt; Enabled
  </code></pre>
  
  <p>It doesn't complain about <code>"ext-gd": "*"</code> or <code>"ext-mbstring": "*"</code>.</p>
  
  <p>PHP 5.6.27</p>