public function getRequiredExtensions()
    {
        $extensions = [];
        if (!$manifest = $this->getManager()->getManifestContents()) {
            return $extensions;
        }

        $data = json_decode($manifest, true);
        $require = (array) array_get($data, 'require');
        foreach ($require as $package => $version) {
            if (mb_substr($package, 0, 4) === 'ext-') {
                $extensions[] = mb_substr($package, 4);
            }
        }

        return $extensions;
    }