Chapter 18. Handling file uploads

Table of Contents
POST method uploads
Common Pitfalls
Uploading multiple files
PUT method support

POST method uploads

PHP is capable of receiving file uploads from any RFC-1867 compliant browser (which includes Netscape Navigator 3 or later, Microsoft Internet Explorer 3 with a patch from Microsoft, or later without a patch). This feature lets people upload both text and binary files. With PHP's authentication and file manipulation functions, you have full control over who is allowed to upload and what is to be done with the file once it has been uploaded.

Note that PHP also supports PUT-method file uploads as used by Netscape Composer and W3C's Amaya clients. See the PUT Method Support for more details.

A file upload screen can be built by creating a special form which looks something like this:

Example 18-1. File Upload Form

  2 <FORM ENCTYPE="multipart/form-data" ACTION="_URL_" METHOD=POST>
  3 <INPUT TYPE="hidden" name="MAX_FILE_SIZE" value="1000">
  4 Send this file: <INPUT NAME="userfile" TYPE="file">
  5 <INPUT TYPE="submit" VALUE="Send File">
  6 </FORM>
The _URL_ should point to a PHP file. The MAX_FILE_SIZE hidden field must precede the file input field and its value is the maximum filesize accepted. The value is in bytes. In this destination file, the following variables will be defined upon a successful upload:

Note that the "$userfile" part of the above variables is whatever the name of the INPUT field of TYPE=file is in the upload form. In the above upload form example, we chose to call it "userfile".

Files will by default be stored in the server's default temporary directory. This can be changed by setting the environment variable TMPDIR in the environment in which PHP runs. Setting it using putenv() from within a PHP script will not work.

The PHP script which receives the uploaded file should implement whatever logic is necessary for determining what should be done with the uploaded file. You can for example use the $file_size variable to throw away any files that are either too small or too big. You could use the $file_type variable to throw away any files that didn't match a certain type criteria. Whatever the logic, you should either delete the file from the temporary directory or move it elsewhere.

The file will be deleted from the temporary directory at the end of the request if it has not been moved away or renamed.