PHP hyperglobal variables include $\_GET, $\_POST, $\_SERVER, $\_SESSION and $\_COOKIE, which are used for data processing in different scenarios respectively. 1. $\_GET is used to obtain URL parameter data, suitable for page navigation but not for sensitive information; 2. $\_POST receives form submissions, which is more secure and suitable for large amounts of or sensitive data; 3. $\_SERVER provides server environment information, such as request method and script path; 4. $\_SESSION saves user status on the server, and requires calling session\_start(); 5. $\_COOKIE is stored in the client, easy to be modified, used for non-sensitive information, and is often used in combination with SESSION to achieve automatic login and other functions.
PHP hyperglobal variables are predefined arrays that can be accessed in any scope of the script. They are very useful for processing form data, session information, server environments, etc. Understanding the functions and usage scenarios of these variables can help write more efficient and secure PHP code.

$_GET
$_GET is used to collect data passed through URL parameters. For example, in example.com?name=John
, the value of name
can be obtained by $_GET['name']
. This method is often used to get data from a link or a simple form submission.
- Data is visible in the URL and is not suitable for delivering sensitive information.
- Only a small amount of data can be processed because there are limits to the URL length.
- Commonly used for page navigation or filtering condition delivery.
It is recommended to avoid passing passwords or other confidential information through the GET method, as this data will be recorded in the browser history or server logs.

$_POST
$_POST is used to receive data submitted through the HTTP POST method, usually from an HTML form. Unlike GET, POST data does not appear in the URL, making it more suitable for passing sensitive information or large amounts of data.
- The data volume limit is much larger than that of GET.
- More suitable for submitting user input, such as login forms or registration information.
- The security is relatively higher, but the input is still required to be verified and filtered.
A common example is the login page, where the username and password entered by the user are submitted to the server for verification through POST.

$_SERVER
$_SERVER contains information about the server and execution environment, such as the file path of the current script, request method, HTTP header, etc. The keys in this array are automatically generated by the server and may vary slightly from server to server.
Commonly used items include:
-
$_SERVER['PHP_SELF']
: The file name of the current script. -
$_SERVER['REQUEST_METHOD']
: Request type (GET, POST, etc.). -
$_SERVER['HTTP_USER_AGENT']
: Client browser information.
Note that some values may be unreliable due to client forgery, such as HTTP_REFERER
or HTTP_USER_AGENT
, so don't rely on them for critical judgments.
$_SESSION and $_COOKIE
These two hyperglobal variables are used to manage user state. $_SESSION is stored on the server, and each user has independent session data; while $_COOKIE is stored in the client browser and is easily modified by the user.
Pay attention to using SESSION:
-
session_start()
must be called before output. - Session data is stored in the server temporary directory by default.
- Suitable for data that needs to be maintained by users' login status, shopping cart, etc.
For COOKIE:
- You can specify the expiration time when setting it, otherwise it is a session cookie and it will be invalid after closing the browser.
- You can set paths and domain names to control the scope of action.
- Because it can be tampered with, it is not recommended to store sensitive information.
Be careful when using the two together. For example, during the login process, you can use SESSION to record the login status and set an encrypted COOKIE as the automatic login credential.
Basically that's it. By mastering the basic uses and precautions of these hyperglobal variables, you can flexibly use them in daily development.
The above is the detailed content of Understanding PHP Superglobals. For more information, please follow other related articles on the PHP Chinese website!

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