I am trying to develop a webapp in Php where users can design items (say a saucer or a table) and choose properties like colour, shape, and then the system has to adapt the display of the image according to the selected properties.
The "customer" side of this is going to be HTML, JavaScript, and some CSS; and how your application stores is could be PHP, ASP.NET, Python or some other server side language. This is relatively easy when it comes to Web Applications
The actual selections are going to on an HTML form, and the requirement of displaying the changes will take some JavaScript to swap images based on the selected items.