Detailed explanation of the usage of 9 super-global arrays of PHP predefined variables_php basics

1.$_SERVER

The $_SERVER super global variable contains information created by the web server, which provides information about the server and client configuration and the current request environment. Depending on the server, the variable value and number of variables in $_SERVER will be different, but generally you can find the variables defined in the CGI1.1 specification. These include:

$_SERVER['HTTP_REFERER']; The URL of the page that guides the user to the current location;

$_SERVER['REMOTE_ADDR']; Customer IP address;

$_SERVER['REQUEST_URI']; The path part of the URL. If the URL is [url]http://www.example.com/blog/apache/index.html[/url], then the URI is /blog/apache/index.html.

$_SERVER['HTTP_USER_AGENT']; The customer's user agent generally provides information about the operating system and browser.

2. $_GET

The $_GET super global variable contains information about the parameters passed using the GET method. If the request URL is [url]http://www.example.com /index.html?cat=apache&id=157[/url], you can use the $_GET super global variable to access the following variables:

$_GET['cat'] = "apache";

$_GET['id'] = "157";

By default, the $_GET superglobal variable is the only way to access variables passed through the GET method.

3. $_POST

The $_POST super global variable contains information about the parameters passed with the POST method.

Through the script subscribe.php, you can use the following POST variables:

$_POST['email'] = " jason@example.com ";

$_POST['pswd'] = "rainyday";

$_POST['subscribe'] = "subscribe!";

Like $_GET, by default, the $_POST superglobal variable is the only way to access POST variables.

4. $_COOKIE

The $_COOKIE super global variable stores information passed to the script through the HTTP cookie. These cookies are generally set by a previously executed PHP script through the PHP function setcookie(). For example, suppose you use setcookie() to store a cookie named example.com with a value of ab2213. This value can be obtained later by calling $_COOKIE['example.com'].

5.$_FILES

The $_FILES super global variable contains information about data uploaded to the server through the POST method. This super global variable is different from other variables. It is a two-dimensional array containing 5 elements. The first subscript indicates the file upload element name of the form; the second subscript is one of five predefined subscripts that describe a certain attribute of the uploaded file:

$_FILES['upload-name']['name']; The file name of the file uploaded from the client to the server;

$_FILES['upload-name']['type']; The MIME type of the uploaded file. Whether this variable is assigned a value depends on the browser's capabilities.

$_FILES['upload-name']['size']; The size of the uploaded file (in bytes);

$_FILES['upload-name']['tmp_name']; The temporary name given to this file before it is moved to its final location after uploading.

$_FILES['upload-name']['error']; Upload status code. Although this variable is named error , this variable is actually filled in on success. It has five possible values:

UPLOAD_ERR_OK File uploaded successfully

UPLOAD_ERR_INI_SIZE The file size exceeds the maximum value specified by the upload_max_filesize directive.

UPLOAD_ERR_FORM_SIZE The file size exceeds the maximum value specified by the MAX_FILE_SIZE hidden form field parameter (optional).

UPLOAD_ERR_PARTIAL Only part of the file was uploaded

UPLOAD_ERR_NO_FILE There is no file specified in the upload form

6.$_ENV

The $_ENV super global variable provides information about the server environment where PHP parses. Variables in this array include:

$_ENV['HOSTNAME'] The host name of the server

$_ENV['SHELL'] system shell

7.$_REQUEST

The $_REQUEST super global variable is an all-rounder that records variables passed to the script through various methods, especially GET, POST and COOKIE. The order of these variables does not depend on the order in which they appear in the send script, but on the order specified by the variables_order configuration directive. It is recommended to use this super variable sparingly because it is not safe enough.

8.$_SESSION

The $_SESSION superglobal variable contains information about all sessions. Registering session information gives you the convenience of being able to reference it throughout your site without having to explicitly pass the data via GET or POST.

9. $GLOBALS

The $GLOBALS super global variable array can be considered a superset of super global variables, including all variables in the global scope. Execute the following code to view all variables in $GLOBALS.

'; <br><br>
print_r ($GLOBALS); <br><br>
print '