Description:
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a) Runtime configuration directives for OPcache 

http://www.php.net/manual/en/opcache.configuration.php

are not included on the page titled "List of php.ini directives".  

http://php.net/manual/en/ini.list.php

b) Extension OPcache is not included in the lists of extensions.

http://www.php.net/manual/en/extensions.membership.php

It is also not included in lists by alphabetical or by state.

 ... extension is bundled with PHP 5.5.0 and later, and is available in PECL for PHP versions 5.2, 5.3 and 5.4

http://www.php.net/manual/en/intro.opcache.php