1&1 is a criminally awful domain registrar, and it appears their hosting is no better. Here is a response from "tech support" to a customer request to enable PEAR on his shared hosting:
> Dear <Firstname> <Lastname>, (Customer ID 123456789)
> Thank you for contacting us.
> Regarding your concern. You need to contact pear support on that matter.
> We refer the website google.com.
> You can also post on there forums.
> If you have any further questions please do not hesitate to contact us.
> Christian Nino Cavan
> Technical Support
> 1&1 Internet