PHP Tutorials - Herong's Tutorial Examples - v5.17, by Herong Yang
Predefined Variables Related to HTTP Requests
This section describes predefined variables, $_GET, $_POST, $_COOKIE, $_REQUEST, and $_SERVER, that contains information included in the HTTP request received by the PHP engine from the Web server.
When the PHP engine is used on a Web server to handle a HTTP request, it converts information submitted in the HTTP request as predefined variables and pass them to PHP script.
1. $_GET - Associate array of HTTP request information submitted with the GET method. By default, all browsers submit HTTP requests with the GET method. Input information collected from Web page forms will be organized into pairs of names and values, which will be attached to the end of the URL in the first line of the HTTP request.
When the PHP engine receives a HTTP request, it will take those pairs of names and values from the end of the request URL and store them in the $_GET array as keys and values.
2. $_POST - Associate array of HTTP request information submitted with the POST method. If a Web page uses the POST method to submit input information collected from its form. The browser will organize input into names and values and attach them as the HTTP request body.
When the PHP engine receives a HTTP request, it will take those pairs of names and values from the request body and store them in the $_POST array as keys and values.
3. $_COOKIE - Associate array of submitted as cookies in the HTTP request. If a browser has cookies received previously from a Web server, it will automatically attach them in the next HTTP request to the same Web server.
When the PHP engine receives a HTTP request, it will take cookie names and cookie values from the request and store them in the $_POST array as keys and values.
4. $_REQUEST - Associate array of all elements from $_GET, $_POST, and $_COOKIE. To help you to get HTTP request input information in a single place, the PHP engine automatically combines all keys and values from $_GET, $_POST, and $_COOKIE into $_REQUEST.
5. $_SERVER - Associate array of information from the Web server and the HTTP request. When the PHP engine receives a HTTP request, it will take other information included in the request and store it in the $_SERVER array as keys and values. For example, the following keys and values represent information received from the HTTP request:
REDIRECT_HANDLER = application/x-httpd-php REDIRECT_STATUS = 200 HTTP_HOST = localhost HTTP_CONNECTION = keep-alive HTTP_UPGRADE_INSECURE_REQUESTS = 1 HTTP_USER_AGENT = Mozilla/5.0 (Windows NT 6.1; Win64; x64) ... HTTP_ACCEPT = text/html,application/xhtml+xml,application/xml;.. HTTP_REFERER = http://localhost/ HTTP_ACCEPT_ENCODING = gzip, deflate, br HTTP_ACCEPT_LANGUAGE = en-US,en;q=0.9 ......
The PHP engine also gathers additional information from the Web server and store it in the $_SERVER array as keys and values. For example, the following keys and values represent information received from the Web server:
SERVER_SIGNATURE = SERVER_SOFTWARE = Apache/2.4.37 (Win64) SERVER_NAME = localhost SERVER_ADDR = ::1 SERVER_PORT = 80 REMOTE_ADDR = ::1 DOCUMENT_ROOT = C:/apache/htdocs REQUEST_SCHEME = http CONTEXT_PREFIX = /cgi-bin-php/ CONTEXT_DOCUMENT_ROOT = /local/php/ ......
The PHP engine also gathers additional information from the operating system where the PHP engine is running and store it in the $_SERVER array as keys and values. For example, the following keys and values represent information received from the operating system:
SystemRoot = C:\windows COMSPEC = C:\windows\system32\cmd.exe PATHEXT = .COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC WINDIR = C:\windows ...
Table of Contents
Introduction and Installation of PHP
PHP Data Types and Data Literals
Variables, References, and Constants
Expressions, Operations and Type Conversions
Conditional Statements - "if" and "switch"
Loop Statements - "while", "for", and "do ... while"
Function Declaration, Arguments, and Return Values
Interface with Operating System
Introduction of Class and Object
Integrating PHP with Apache Web Server
►Retrieving Information from HTTP Requests
►Predefined Variables Related to HTTP Requests
Operating System Information in $_SERVER
Web Server Information in $_SERVER
Information in $_GET and $_REQUEST
Registering $_REQUEST Keys as Global Variables
Creating and Managing Sessions in PHP Scripts
Sending and Receiving Cookies in PHP Scripts
Controlling HTTP Response Header Lines in PHP Scripts
MySQL Server Connection and Access Functions
Functions to Manage Directories, Files and Images
SOAP Extension Function and Calling Web Services
SOAP Server Functions and Examples
Localization Overview of Web Applications
Using Non-ASCII Characters in HTML Documents
Using Non-ASCII Characters as PHP Script String Literals
Receiving Non-ASCII Characters from Input Forms
"mbstring" Extension and Non-ASCII Encoding Management
Managing Non-ASCII Character Strings with MySQL Servers
Parsing and Managing HTML Documents
Configuring and Sending Out Emails
Managing PHP Engine and Modules on macOS