PHP Superglobals

Superglobals in PHP are predefined variables that are always accessible from any scope of a script. They provide valuable information about the server, client, and environment. Here are some of the most commonly used PHP superglobals:

1. $_GET:

• Contains variables passed to the current script via the URL parameters (query string).
• Data is accessible using keys in the associative array format.

// URL: http://example.com/?name=John&age=30
echo $_GET['name']; // Output: John
echo $_GET['age']; // Output: 30

2. $_POST:

• Contains variables passed to the current script via HTTP POST method.
• Data is accessible using keys in the associative array format.

echo $_POST['username'];
echo $_POST['password'];

3. $_REQUEST:

• Contains data from both $_GET and $_POST as well as cookies.
• Data is accessible using keys in the associative array format.

echo $_REQUEST['name'];

4. $_SESSION:

• Contains session variables created and maintained on the server.
• Used to store user-specific information across multiple pages.

session_start();
$_SESSION['username'] = 'John';

5. $_COOKIE:

• Contains cookies sent by the client to the server.
• Data is accessible using keys in the associative array format.

echo $_COOKIE['username'];

6. $_FILES:

• Contains information about uploaded files via HTTP POST method.
• Provides details such as file name, type, size, etc.

echo $_FILES['file']['name'];
echo $_FILES['file']['type'];

7. $_SERVER:

• Contains information about the server environment and the current script.
• Provides details such as server name, script name, request method, etc.

echo $_SERVER['SERVER_NAME'];
echo $_SERVER['REQUEST_METHOD'];

8. $_ENV:

• Contains variables from the environment.
• Provides details such as the current user, home directory, etc.

echo $_ENV['USER'];
echo $_ENV['HOME'];

Superglobals are extremely useful in PHP programming as they provide a convenient way to access and manipulate various aspects of the server, client, and environment. However, it’s essential to handle them with care, especially when dealing with user input, to prevent security vulnerabilities such as SQL injection and cross-site scripting (XSS) attacks.