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:
Esimerkki 19-1. File Upload Form <form enctype="multipart/form-data" action="_URL_" method="post">
<input type="hidden" name="MAX_FILE_SIZE" value="1000">
Send this file: <input name="userfile" type="file">
<input type="submit" value="Send File">
</form> |
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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.
| Varoitus |
The MAX_FILE_SIZE is advisory to the browser. It is easy to
circumvent this maximum. So don't count on it that the browser
obeys you wish! The PHP-settings for maximum-size, however,
cannot be fooled.
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Variables defined for uploaded files differs depends on PHP
version and configuration. Following variables will be defined
within the destination script upon a successful upload. When track_vars is enabled,
$HTTP_POST_FILES/$_FILES array is initialized. Finally, related
variables may be initialized as globals when
register_globals
is turned on. However, use of globals is not recommended anymore.
Huomaa:
track_vars is always on
from PHP 4.0.3. From PHP 4.1.0 or later, $_FILES may be used
instead of
$HTTP_POST_FILES. $_FILES is
always global, so global should not be used
for $_FILES in function scope.
$HTTP_POST_FILES/$_FILES is
provided to contain the uploaded file information.
The contents of $HTTP_POST_FILES are as
follows. Note that this assumes the use of the file upload name
'userfile', as used in the example script above:
- $HTTP_POST_FILES['userfile']['name']
The original name of the file on the client machine.
- $HTTP_POST_FILES['userfile']['type']
The mime type of the file, if the browser provided this
information. An example would be
"image/gif".
- $HTTP_POST_FILES['userfile']['size']
The size, in bytes, of the uploaded file.
- $HTTP_POST_FILES['userfile']['tmp_name']
The temporary filename of the file in which the uploaded file
was stored on the server.
Huomaa:
PHP 4.1.0 or later supports a short track variable
$_FILES. PHP 3 does not support
$HTTP_POST_FILES.
When register_globals
is turned on in php.ini the available variables
are as follows. Note that the following variable names assume the
use of the file upload name 'userfile', as used in the example
script above:
$userfile - The temporary filename in which
the uploaded file was stored on the server machine.
$userfile_name - The original name or path
of the file on the sender's system.
$userfile_size - The size of the uploaded
file in bytes.
$userfile_type - The mime type of the file
if the browser provided this information. An example would be
"image/gif".
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".
Huomaa:
register_globals = On is not recommended for
security and performance reason.
Files will by default be stored in the server's default temporary
directory, unless another location has been given with the upload_tmp_dir directive in
php.ini. The server's default directory 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. This environment variable can also be used
to make sure that other operations are working on uploaded files,
as well.
Esimerkki 19-2. Validating file uploads
The following examples are for versions of PHP 4 greater than
4.0.2. See the function entries for
is_uploaded_file() and
move_uploaded_file().
<?php
// In PHP 4.1.0 or later, $_FILES should be used instead of $HTTP_POST_FILES.
if (is_uploaded_file($HTTP_POST_FILES['userfile']['tmp_name'])) {
copy($HTTP_POST_FILES['userfile']['tmp_name'], "/place/to/put/uploaded/file");
} else {
echo "Possible file upload attack. Filename: " . $HTTP_POST_FILES['userfile']['name'];
}
/* ...or... */
move_uploaded_file($HTTP_POST_FILES['userfile']['tmp_name'], "/place/to/put/uploaded/file");
?> |
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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
$HTTP_POST_FILES['userfile']['size'] variable
to throw away any files that are either too small or too big. You
could use the
$HTTP_POST_FILES['userfile']['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.
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