Specifications
Common Problems
There are a few things to keep in mind when performing file uploads.
• The previous example assumes that users have been authenticated elsewhere. You
shouldn’t allow just anybody to upload files on to your site.
• If you are allowing untrusted or unauthenticated users to upload files, it’s a good idea to
be pretty paranoid about the contents of them. The last thing you want is a malicious
script being uploaded and run. You should be careful, not just of the type and contents of
the file as we are here, but of the filename itself. It’s a pretty good idea to rename
uploaded files to something you know to be “safe.”
• If you are using an NT or other Windows-based machines, be sure to use
\\ instead of \
in file paths as usual.
• If you are having problems getting this to work, check out your php.ini file. You will
need to have set the upload_tmp_dir directive to point to some directory that you have
access to. You might also need to adjust the memory_limit directive if you want to
upload large files—this will determine the maximum file size in bytes that you can
upload.
• If PHP is running in safe mode, you will get an error message about being unable to
access the temporary file. This can only be fixed either by not running in safe mode or
by writing a non-PHP script that copies the file to an accessible location. You can then
execute this script from your PHP script. We’ll look at how to execute programs on the
server from PHP toward the end of this chapter.
Using Directory Functions
After the users have uploaded some files, it will be useful for them to be able to see what’s
been uploaded and manipulate the content files.
PHP has a set of directory and file system functions that are useful for this purpose.
Reading from Directories
First, we’ll implement a script to allow directory browsing of the uploaded content. Browsing
directories is actually very straightforward in PHP. In Listing 16.3, we show a simple script
that can be used for this purpose.
Advanced PHP Techniques
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