Supported Versions: PHP 4, PHP 5, PHP 7, PHP 8
Checks whether a constant with the given name exists
<?php defined(string $constant_name): bool
<?php     {

        $ignorePassiveAddress = $options->ignorePassiveAddress();



        if ( ! is_bool($ignorePassiveAddress) || ! defined('FTP_USEPASVADDRESS')) {

            return;

        }