PHP has five most commonly used hyperglobal variables, namely $\_GET, $\_POST, $\_SERVER, $\_SESSION, and $\_COOKIE. ① $\_GET is used to obtain parameters in the URL, suitable for non-sensitive data transmission such as paging and filtering, but attention should be paid to input verification; ② $\_POST is used to receive sensitive data submitted by form, such as login information, which needs to be prevented from SQL injection and XSS attacks; ③ $\_SERVER provides information about the server and script execution environment, such as the current script name, user IP and request method. Before use, check whether the key exists; ④ $\_SESSION is used to maintain user status across pages. Session\_start() must be called first when using it, and sensitive information should not be stored; ⑤ $\_COOKIE is used to read client cookies. When setting, pay attention to security flags and expiration time to avoid storing sensitive data. These variables are very basic and important in PHP development. Rational use can improve development efficiency, while paying attention to security issues.
PHP has several very practical hyperglobal variables that are accessible anywhere in the script, whether inside a function, in a class, or in a namespace. They are mainly used for common tasks such as obtaining server information, processing form data, and managing sessions. Here are some of the most commonly used hyperglobal variables and their usage scenarios.
$_GET is used to get parameters in the URL
When you pass parameters through URLs, such as index.php?id=123&name=test , this data will be stored in the $_GET array. You can get the corresponding value by the key name:
echo $_GET['id']; // Output 123
Recommended usage:
- Suitable for simple data transfer, such as paging, filtering conditions, etc.
- Not suitable for passing sensitive information, because the parameters will be displayed in the URL.
- Pay attention to verifying and filtering the input to prevent security issues.
$_POST is used to receive data submitted by the form
When an HTML form is submitted using method="post" , the data is stored in $_POST . For example, after submitting a login form, you can get the username and password like this:
$username = $_POST['username']; $password = $_POST['password'];
Recommended usage:
- Better to process sensitive data, because the data is not exposed to the URL.
- It is often used in scenarios such as user login, registration, file upload, etc.
- Also, clean and verify the input to prevent SQL injection or XSS attacks.
$_SERVER Provides information about the server and execution environment
This array contains a lot of information about the server and the current script execution. For example, get the file name of the current script:
echo $_SERVER['PHP_SELF']; // Output/index.php
Other common usages:
- Get user IP:
$_SERVER['REMOTE_ADDR'] - Get request method:
$_SERVER['REQUEST_METHOD'] - Get server domain name:
$_SERVER['HTTP_HOST']
hint:
- Some values may vary depending on the server configuration.
- It is best to check whether it exists before using it, such as using
isset()orarray_key_exists().
$_SESSION is used to maintain user status across pages
If you need to keep the user logged in between multiple pages, you need to use $_SESSION . Start the session before use:
session_start(); $_SESSION['user_id'] = 123;
In another page, you can also access this value:
session_start(); echo $_SESSION['user_id']; // Output 123
Notes:
-
session_start()is called before each use. - Do not directly store sensitive information in session, such as passwords.
- session data is stored on the server by default and will not be exposed to users.
$_COOKIE Cookie used to read client
If the browser sends a cookie, you can read it through $_COOKIE . For example, you have set a cookie with the user login status before:
setcookie('user_logged_in', 'true', time() 3600);
In subsequent requests, you can read it like this:
if (isset($_COOKIE['user_logged_in'])) {
echo 'User logged in';
}Tips for use:
- Cookies exist on the client side, so don't put sensitive data.
- When setting cookies, pay attention to the expiration time and path, otherwise it may not be read.
- Security flags such as
HttpOnlyandSecurecan be set to enhance security.
These hyperglobal variables are one of the most basic and important tools in PHP development. Although they are simple to use, the security and mechanism issues involved cannot be ignored. As long as it is used reasonably, it can achieve twice the result with half the effort in development.
Basically that's it.
The above is the detailed content of PHP's Superglobal Variables. For more information, please follow other related articles on the PHP Chinese website!
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