Nelmio\SecurityBundle\ExternalRedirect\WhitelistBasedTargetValidator::__construct PHP Method

    public function __construct($whitelist = null)
    {
        if (is_array($whitelist)) {
            if ($whitelist) {
                $whitelist = array_map(function ($el) {
                    return preg_quote(ltrim($el, '.'));
                }, $whitelist);
                $whitelist = '(?:.*\\.' . implode('|.*\\.', $whitelist) . '|' . implode('|', $whitelist) . ')';
            } else {
                $whitelist = null;
            }
        }
        $this->whitelist = $whitelist;
    }