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PHP Superglobals

PHP superglobals are built-in global arrays in PHP that provide access to various types of data throughout your application. They are available in all scopes and can be used to access or manipulate data like form inputs, session variables, cookies, and more. Here’s a rundown of the main PHP superglobals with examples:

$_GET: Contains data sent via the URL query string (HTTP GET method).

// URL: example.com/index.php?name=John&age=25
echo $_GET['name']; // Outputs: John
echo $_GET['age'];  // Outputs: 25

$_POST: Contains data sent via the HTTP POST method (usually from forms).

// Assume a form was submitted with a POST request
echo $_POST['username']; // Outputs the value of the 'username' field
echo $_POST['password']; // Outputs the value of the 'password' field

$_REQUEST: Contains data from both $_GET and $_POST, and also $_COOKIE.

// Combining GET and POST data
echo $_REQUEST['name']; // Outputs the 'name' value from GET or POST

$_SERVER: Contains information about the server environment and HTTP headers.

echo $_SERVER['HTTP_USER_AGENT']; // Outputs the user's browser information
echo $_SERVER['REQUEST_METHOD'];  // Outputs the request method (GET, POST, etc.)

$_SESSION: Used to store session variables. Sessions must be started with session_start() before using $_SESSION.
```
session_start();
$_SESSION['username'] = 'JohnDoe';
echo $_SESSION['username']; // Outputs: JohnDoe
```

$_COOKIE: Contains cookies sent by the client.

// Set a cookie first
setcookie('user', 'JohnDoe', time() + 3600); // Expires in 1 hour
echo $_COOKIE['user']; // Outputs: JohnDoe (if cookie is set)

$_FILES: Contains information about files uploaded through a form.

// Assuming a form with file upload is submitted
echo $_FILES['file']['name']; // Outputs the name of the uploaded file
echo $_FILES['file']['size']; // Outputs the size of the uploaded file

$_ENV: Contains environment variables.

echo $_ENV['PATH']; // Outputs the system path environment variable

$_GLOBALS: An associative array containing all global variables.

$a = 10;
function test() {
    global $a;
    echo $a; // Outputs: 10
}
test();

These superglobals provide a way to access data across different parts of your PHP application, making it easier to handle form inputs, manage sessions, and interact with the server and environment.

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