public function get($key, $a = null)
    {
        if ($a !== null) {
            $this->triggerError(
                "Using deprecated API: use \$config->get('$key.$a') instead",
                E_USER_WARNING
            );
            $key = "$key.$a";
        }
        if (!$this->finalized) {
            $this->autoFinalize();
        }
        if (!isset($this->def->info[$key])) {
            // can't add % due to SimpleTest bug
            $this->triggerError(
                'Cannot retrieve value of undefined directive ' . htmlspecialchars($key),
                E_USER_WARNING
            );
            return;
        }
        if (isset($this->def->info[$key]->isAlias)) {
            $d = $this->def->info[$key];
            $this->triggerError(
                'Cannot get value from aliased directive, use real name ' . $d->key,
                E_USER_ERROR
            );
            return;
        }
        if ($this->lock) {
            list($ns) = explode('.', $key);
            if ($ns !== $this->lock) {
                $this->triggerError(
                    'Cannot get value of namespace ' . $ns . ' when lock for ' .
                    $this->lock .
                    ' is active, this probably indicates a Definition setup method ' .
                    'is accessing directives that are not within its namespace',
                    E_USER_ERROR
                );
                return;
            }
        }
        return $this->plist->get($key);
    }