MySQL Cookbook, 2nd Edition

Processing File Uploads

Problem

You want to allow files to be uploaded to your web server and stored in your database.

Solution

Present the user with a web form that includes a file field. When the user submits the form, extract the file and store it.

Discussion

One special kind of web input is an uploaded file. A file is sent as part of a post request, but it’s handled differently from other post parameters, because a file is represented by several pieces of information such as its contents, its MIME type, its original filename on the client, and its name in temporary storage on the web server host.

To handle file uploads, you must send a special kind of form to the user; this is true no matter what API you use to create the form. When the user submits the form, the operations that check for and process an uploaded file are API-specific.

To create a form that enables files to be uploaded, the opening <form> tag should specify the post method and must also include an enctype (encoding type) attribute with a value of multipart/form-data:

<form method="post" enctype="multipart/form-data" action="script_name">

If the form is submitted using the application/x-www-form-urlencoded encoding type, file uploads will not work properly.

To include a file upload field in the form, use an <input> element of type file. For example, to present a 60-character file field named upload_file, the element looks like this:

<input type="file" name="upload_file" size="60" />

The browser displays this field as a text ...