For developers creating an application using PHP, you can connect to Microsoft SQL Azure Database. MSDN has published a walkthrough article on how to do this. The great thing about this is that you can run your PHP application on your own server, with a hoster, or within Windows Azure. In any one of those deployment choices, you can access SQL Azure database without any changes.
You can connect to Microsoft SQL Azure Database by using PHP and the SQL Server Driver for PHP starting with version 1.1. This topic shows how to create a PHP application within a Windows Azure Web CGI Role that connects to SQL Azure Database. Follow the steps in the Getting Started section of the SQL Server Driver for PHP documentation to prepare your server for developing with PHP and SQL Server.