Personal insights on predefined variables in PHP

What are the predefined variables in PHP?

#Predefined variables are also called super global variables.

definition:

Predefined variables are variables defined by the system itself and can be used directly. Predefined variables all exist in the form of arrays.

There are many kinds of predefined PHP, including our get, post, etc., which are all predefined variables of PHP. Let's take a look at how these predefined variables are used.

1.$_GET variable

$_GET variable will be "automatically stored" (saved/loaded) submitted GET data into a file.

The GET data is the data submitted when a page is requested in "get" mode.

Code Demonstration

Create a form with two input boxes that can output numbers and submit

        姓名:
        

        年龄:
        

        

$name = $_GET['username'];
$age = $_GET['age'];
echo "
姓名为:".$name;
echo "
年龄为:".$age;

2 The .$_POST

#$_POST variable will "automatically store" (save/load) the POST data submitted to a file.

The POST data is the data submitted in the "post" mode in a form

Code demonstration

There is a form with two inputs Box, you can fill in numbers, there is a "submit button", click submit, you can calculate their sum and output

        数字1
        
        
 数字2
        
        

        

$num1 = $_POST['num1'];
$num2 = $_POST['num2'];
$result = $num1 + $num2;
echo "相加计算的结果为：",$result;

3.$_REQUEST

Represents the collection of data submitted by the browser through the "get" method or the "post" method.

That is: it can receive both get data and post data!

Usually, a form only submits one form of data, either get data or post data!

4.$_SERVER

It represents some "basic information" or system information on the client or server side in any request

Commonly used ones are:

PHP_SELF: Indicates the currently requested web page address (excluding the domain name part)

SERVER_NAME: Indicates the current Requested server name

SERVER_ADDR: Indicates the currently requested server IP address

DOCUMENT_ROOT: Indicates the currently requested website physical path (apache settings site That one)

REMOTE_ADDR: Indicates the IP address of the currently requested client

SCRIPT_NAME: Indicates the current web page address

Summary:

In this way, we can obtain information such as user session, user operating system environment and local operating system environment through these predefined variables.

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