Dependency Isolation and Declaration in PHP

What's the best way to achieve complete dependency declaration and isolation in a PHP web app? I already know about Composer, but that's only the declaration part and I don't think it goes far enough. I'd like to include as much of the following as I can: PHP extensions (e.g. mcrypt, imagick, apc), the php.ini config and configs for extensions, PECL packages, and ideally even my Apache config files. Is there something like Ruby's bundle exec for PHP?