MySQL Cookbook, 2nd Edition

Serving Query Results for Download

Problem

You want to send database information to a browser for downloading rather than for display.

Solution

Unfortunately, there’s no good way to force a download. A browser will process information sent to it according to the Content-Type: header value, and if it has a handler for that value, it will treat the information accordingly. However, you may be able to trick the browser by using a “generic” content type for which it’s unlikely to have a handler.

Discussion

Earlier sections of this chapter discuss how to incorporate the results of database queries into web pages, to display them as paragraphs, lists, tables, or images. But what if you want to produce a query result that the user can download to a file instead? It’s not difficult to generate the response itself: send a Content-Type: header preceding the information, such as text/plain for plain text, image/jpeg for a JPEG image, or application/pdf or application/msexcel for a PDF or Excel document. Then send a blank line and the content of the query result. The problem is that there’s no way to force the browser to download the information. If it knows what to do with the response based on the content type, it will try to handle the information as it sees fit. If it knows how to display text or images, it will. If it thinks it’s supposed to give a PDF or Excel document to a PDF viewer or to Excel, it will. Most browsers enable the user to select a download explicitly (for example, by right-clicking ...