Map with Custom Radius Pins

Evening, hopefully im in the right place, currently creating a website and want to set up a interactive map (of sorts) where a user will enter their post code and select a radius (in miles) and then the map will bring ( with pins on the map for ease of identification) up a list of places in that area from a defined database. Currently have no idea how to do this. I would appreciate help if this has been done before or even a point in a direction to get started. Thanks in advance.