PHP

PHP

🌐 Super Globals in PHP

Super Globals are built-in predefined associative arrays in PHP that are always accessible in all scopes throughout a script. You don't need to define them or declare global $variable to access them inside functions, methods, or files.

  • Basic Concept: Super globals automatically capture data from user requests, forms, browser headers, cookies, active sessions, and server environments.

⚡ Most Commonly Used Super Global Variables

1️⃣ $GLOBALS
A superglobal array used to access global variables from anywhere in the PHP script (even inside functions or methods).

PHP
$a = 10;

function test() {
    // Accessing global variable $a inside local scope
    echo $GLOBALS['a'];
}

test(); // Outputs: 10

2️⃣ $_SERVER
Holds information about headers, paths, script locations, and server execution environments.

PHP
echo $_SERVER['SERVER_NAME']; // Host name of the server
echo $_SERVER['REQUEST_METHOD']; // GET, POST, etc.
echo $_SERVER['SCRIPT_NAME']; // Path of current script

3️⃣ $_GET
Collects data sent via URL parameters (query string). Visible in the address bar and used for non-sensitive data transfers.

PHP
// Example URL: site.com/index.php?isim=Ali
if (isset($_GET['isim'])) {
    echo "Hello, " . $_GET['isim']; // Outputs: Hello, Ali
}

4️⃣ $_POST
Collects data sent via HTTP POST method (typically HTML form submissions). Values are hidden in the request body, making it ideal for passwords and sensitive inputs.

PHP
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $email = $_POST['email'];
    echo "Submitted email: " . $email;
}

5️⃣ $_REQUEST
Combines the contents of $_GET, $_POST, and $_COOKIE into a single array.

  • Best Practice: Explicitly use $_GET or $_POST instead of $_REQUEST for clarity and security.

PHP
$name = $_REQUEST['isim'];

6️⃣ $_FILES
An associative array containing items uploaded via HTTP POST multipart form requests (file name, MIME type, size, temporary path, and error status).

PHP
$fileName = $_FILES['resim']['name'];
$fileTmp = $_FILES['resim']['tmp_name'];
$fileSize = $_FILES['resim']['size'];

7️⃣ $_COOKIE
Retrieves values stored on the client's browser using HTTP Cookies.

PHP
if (isset($_COOKIE['kullanici'])) {
    echo "Welcome back, " . $_COOKIE['kullanici'];
}

8️⃣ $_SESSION
Stores data across multiple pages for an individual user on the server side. Requires session_start() prior to output.

PHP
session_start();

$_SESSION['user'] = "Ali";
echo "Active Session User: " . $_SESSION['user'];

📊 Quick Summary Table

Here is a reference summary for PHP superglobals:

Variable Purpose & Description
$GLOBALS Access global variables from anywhere in script scope.
$_SERVER Server environment, headers, and execution information.
$_GET Collects parameters passed in the URL.
$_POST Collects hidden form payloads via HTTP POST.
$_REQUEST Combined array of GET, POST, and COOKIE data.
$_FILES Contains uploaded file payloads and metadata.
$_COOKIE Retrieves persistent client-side browser cookies.
$_SESSION Manages stateful user session data on the server.

  • 📝 Summary Takeaways

  • Superglobals are case-sensitive and always start with an underscore except for $GLOBALS.
  • Always sanitize and validate inputs from $_GET, $_POST, and $_COOKIE before processing.
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