In the past, Microsoft has said that its ASP.NET AJAX (Atlas) framework could be used sans Microsoft development tools. Particularly, the client-side library in ASP.NET AJAX can interact with several web-based programming languages as it consists of nothing more than JavaScript. That being said, one industrious Microsoft dev has gone ahead and created a library called "PHP for Microsoft AJAX Library" that allows PHP developers to easily interact with Microsoft's rich client framework.
Download : codeplex.com/phpmsajax
Source : arstechnica.com/journals/microsoft.ars
