What are the predefined arrays in php

There are 9 predefined arrays in php: 1. "$_SERVER" is an array containing header information, path and script location; 2. "$_GET" is composed of variables passed through the GET method array; 3. "$_POST" is an array composed of variables passed through the POST method; 4. "$_FILES", etc.

The operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer

Predefined array

Starting from PHP 4.1.0, PHP provides a set of additional predefined arrays. These array variables contain data from the web server, client, running environment and user input. These arrays are very special. , often called automatic global variables or "super" global variables. It is a special kind of array, and there is no difference in the operation method; instead of declaring them, they exist by default in every PHP script. Because users do not need to customize them in PHP, they should avoid having the same name as predetermined global variables when customizing variables. ; They automatically take effect in the global scope, that is, they can be used directly in the function without using the global keyword to access them.

Predefined array	Description
$_SERVER	Variables are set by the web server or are directly associated with the execution environment of the current script
$_ENV	Variables submitted by the execution environment to the script
$_GET	Variables submitted to the script via the URL request
$_POST	Submitted via the http post method Variables to the script
$_REQUEST	Variables submitted to the script via the get, post and cookie mechanisms, so the array is not trustworthy
$_FILES	Variables submitted to the script via http, post file upload
$_COOKIE	via http cookies method Variables submitted to the script
$_SESSION	Variables currently registered to the script session
$GLOBALS	Contains a reference to a variable that is valid in the global variable scope of each current script. The key name of this array is the name of the global variable

1. Server variable: $_SERVER

$_SERVER is an array containing header information, path and script location. The entities of the array are created by the web server, and there is no guarantee that all servers can generate all information. The server may ignore some information, or generate some other new information. Like other superglobal arrays, this is an automatic global variable that is available in all scripts. There is no need to use the global keyword to access it in functions or object methods.

2. Environment variables: $_ENV

$_ENV The contents of the array are changed from the environment variables in the server where PHP is located to PHP when the PHP parser is running. of global variables. Many of them are determined by the system on which PHP is running. A complete list is not possible. You need to check the system documentation of the server where PHP is running to determine its specific environment variables.

3. URL GET variables: $_GET

$_GET array is also a super global variable array, which is an array composed of variables passed through the URL GET method. It is an external variable, that is, the parameters passed in the URL or form's GET method are obtained through $_GET super-global data in the server page.

4. HTTP POST variables: $_POST

$_POST array is an array composed of variables passed through the HTTP POST method. Either the $_POST or $_GET arrays can save the variables submitted by the form. Which array is used depends on whether the method attribute in the form tag when submitting the form uses post or get. But using the $_POST array can only access form data submitted with the post method.

5. request variable: $_REQUEST

This associative array contains all the contents of $_GET, $_POST and $_COOKIE, but its speed is relatively slow, so it is not Recommended Use.

6. HTTP file upload variable: $_FILES

When uploading files using the file input field of the form, you must use post submission. However, in the server file, the contents of the file field in the form cannot be obtained through the $_POST superglobal array. The $_FILES superglobal variable is an array of uploaded file items passed through the post method. $_FILES is a two-dimensional array that contains 5 subarray elements. The first subscript is the name of the file input field in the form, and the second subscript is used to describe the attributes of the uploaded file.

7. HTTP Cookies: $_COOKIE

$_COOKIE super global array is a variable submitted to the script via the HTTP Cookies method. Usually these cookies are set to the client browser by a previously executed PHP script through the setCookies() function. When the PHP script extracts a cookie from the client browser, it will automatically convert it into a variable, which can be passed through this The $_COOKIE superglobal array and cookie name are used to access the specified cookie value.

8. Session variable: $_SESSION

Session control uses session on the server side to track users. When the session_start() function is used to open the session on the server page, You can use the $_SESSION array to register global variables, and users can access this member information throughout the website.

9. Global variables: $GLOBALS

$GLOBALS is an array composed of all defined global variables, and the variable name is the index of the array.

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