web based file manager

We are trying to make a web based application for storing documents, however this is not a conventional web based file manager application. We want to use MongoDB and PHP based web-service. The application should be ultra secure. JSON should be the mode of data transfer between the HTML client (JQuery Ajax) , PHP webservice and MongoDB. The file types should be limited to images (png, jpeg, gif), word, excel, pdf. Should restrict the file size to 10 MB as MongoDB document size cannot exceed 16MB (for a single document) Your responsibilities: - Review business requirements - Perform a technical analysis of requirements - Produce a solid, detailed technical design - Write clean, modular, robust code to implement the desired requirements - Contribute ideas for making the application better and easier to use Your qualifications: - Programming languages: PHP, JQuery, MongoDB, HTML, CSS - A work style that is extremely detail oriented