There are currently two ways of developing stand alone PHP applications. Both options are only available for Windows platforms (XP and Greater). PHP-GTK is a development that utilizes the GTK visual...
You can check OpenCart for this. It is a CRM which give a fully functional eCommerce app with admin dashboard, and you can customize it base on your requirement. Hope this help.
PHP can be used to create almost anything when it comes to web applications. Applications could be created to do: CMS Email Web games Social networking Photo gallery's Video websites Graphs Database...