Web application to create a personalised postcard

I have a project where I have to design a web application that could let the user upload a photo and create a postcard out of it with the options of redimensiom or rotate the original picture and add text and then export it to a pdf file. The main website ismainly using php.

I would like to have some hints on how to start this and what technologies would you recommend to achieve this task? Thx