php - How to preprocess a local CSV file before uploading to a server?

Question

I am trying to set up a web page where trusted users can upload local CSV files that will be parsed, validated, reviewed by the users, and then inserted into various tables on a MySQL database.

The rest of the site is written using PHP and jQuery. I know how to read a CSV file into PHP and generate a query. The problem is that the validation and parsing of the file is interactive-- the user needs to be asked for various information about the data, match up columns from the file with fields in the database, and be given the opportunity to review and update their answers until they're sure everything is correct.

It seems kind of 1990's to reload the whole page every time the user changes something, so I assumed that AJAX would be the way to do it client-side, but it seems that opening local files is specifically prevented by browsers for "security reasons".

My question is:

Is there a generally accepted pattern for securely and efficiently letting a user make decisions based on the contents of a file before actually uploading the file to the server? Or do people really just send dozens of POST requests in such situations?

By the way, we do not use Windows or anything closed-source, so unfortunately the solution cannot rely on Internet Explorer or ActiveX.

Thanks.

Answer 1

You don't need to make any request to the server if you use the javascript FileReader API available starting from firefox 3.6 and Chrome 7. Fortunately really interesting articles exist that explain quite clearly how the API works.

http://www.html5rocks.com/en/tutorials/file/dndfiles/

If you have concerns about the support for the API in the different browsers it is displayed at the end of this other article:

https://developer.mozilla.org/en/DOM/FileReader

I've recently used this API for uploading both text and binary files so don't hesitate to get back to me if you decide you want to try it and you have any doubt.