PHP Web Related Variables

In PHP 4.2.0 and after, the default setting for register_globals is off. With register_globals off, all the various variables that are usually available directly in the global symbol table are now available via individual superglobal arrays. There is a limited set of superglobals and they cannot be created from a user-level script. The superglobal array to use depends on the source of the variable. Here is the list:

$_GET

GET-method variables. These are the variables supplied directly in the URL. For example, with http://www.example.com/script.php?a=1&b=2, $_GET['a'] and $_GET['b'] are set to 1 and 2, respectively.

$_POST

POST-method variables. Form field data from regular POST-method forms.

$_COOKIE

Any cookies the browser sends end up in this array. The name of the cookie is the key and the cookie value becomes the array value.

$_REQUEST

This array contains all of these variables (i.e., GET, POST, and cookie). If a variable appears in multiple sources, the order in which they are imported into $_REQUEST is given by the setting of the variables_order php.ini directive. The default is 'GPC', which means GET-method variables are imported first, then POST-method variables (overriding any GET-method variables of the same name), and finally cookie variables (overriding the other two).

$_SERVER

These are variables set by your web server. Traditionally things like DOCUMENT_ROOT, REMOTE_ADDR, REMOTE_PORT, SERVER_NAME, SERVER_PORT, and many others. To get a full list, have a look at your phpinfo( ) output, or run a script like the following to have a look:

<?php

foreach($_SERVER as $key=>$val) {

echo '$_SERVER['.$key."] = $val<br>\n";

}

?>

$_ENV

Any environment variables that were set when you started your web server are available in this array.

$_FILES

For RFC 1867-style file uploads the information for each uploaded file is available in this array. For example, for a file upload form containing:

<input name="userfile" type="file">

The $_FILES array will look something like this:

$_FILES['userfile']['name'] => photo.png

$_FILES['userfile']['type'] => image/png

$_FILES['userfile']['tmp_name'] => /tmp/phpo3kdGt

$_FILES['userfile']['error'] => 0

$_FILES['userfile']['size'] => 158918

Note that the 'error' field is new for PHP 4.2.0 and the values are: 0 (no error, file was uploaded); 1 (the uploaded file exceeds the upload_max_filesize directive in php.ini); 2 (the uploaded file exceeds the MAX_FILE_SIZE directive that was specified in the HTML form); 3 (the actual number of bytes uploaded was less than the specified upload file size); and 4 (no file was uploaded).

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