PHP Superglobals $_GET, $_POST, $_SESSION: Tutorial, Examples, FAQs & Interview Tips

Superglobals are built-in variables that are always accessible regardless of scope - inside functions, classes, or files. They are prefixed with $_.

$_GET and $_POST

$_GET collects data sent via URL query strings. $_POST collects data sent via HTTP POST (form submissions). $_REQUEST contains both.

$_GET and $_POST

<?php
// URL: example.com/page.php?name=Alice&age=30
$name = $_GET['name'] ?? 'Guest';
$age  = $_GET['age']  ?? 0;
echo "Name: $name, Age: $age";

// POST data from a form
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    $username = htmlspecialchars($_POST['username'] ?? '');
    $password = $_POST['password'] ?? '';
    echo "Username: $username";
}

// $_REQUEST combines GET, POST, and COOKIE
$search = $_REQUEST['q'] ?? '';
echo "Search: $search";
?>

$_SERVER

$_SERVER contains information about the server environment, headers, and the current request.

$_SERVER

<?php
echo $_SERVER['SERVER_NAME'];    // e.g. localhost
echo $_SERVER['HTTP_HOST'];      // e.g. www.example.com
echo $_SERVER['SCRIPT_NAME'];    // e.g. /index.php
echo $_SERVER['REQUEST_METHOD']; // GET or POST
echo $_SERVER['REMOTE_ADDR'];    // visitor's IP address
echo $_SERVER['HTTP_USER_AGENT']; // browser info
echo $_SERVER['QUERY_STRING'];   // everything after ?
echo $_SERVER['DOCUMENT_ROOT'];  // server root path
echo $_SERVER['PHP_SELF'];       // current script path
?>

$_FILES, $_ENV, $_COOKIE, $_SESSION

Other Superglobals

<?php
// $_FILES - file upload info
// <input type="file" name="photo">
$fileName = $_FILES['photo']['name']     ?? '';
$fileSize = $_FILES['photo']['size']     ?? 0;
$fileTmp  = $_FILES['photo']['tmp_name'] ?? '';
$fileErr  = $_FILES['photo']['error']    ?? 1;

if ($fileErr === UPLOAD_ERR_OK) {
    move_uploaded_file($fileTmp, "uploads/$fileName");
    echo "Uploaded: $fileName";
}

// $_ENV - environment variables
$dbHost = $_ENV['DB_HOST'] ?? 'localhost';

// $_COOKIE - read a cookie
$theme = $_COOKIE['theme'] ?? 'light';
echo "Theme: $theme";

// $_SESSION - read session data
session_start();
$_SESSION['user'] = 'Alice';
echo $_SESSION['user']; // Alice
?>

Key Takeaways

PHP superglobals are built-in variables available in all scopes without needing global keyword.
Always sanitize and validate data from \, \, and \ before using it.
Use filter_input() or filter_var() to safely retrieve and validate superglobal values.
\ requires session_start() to be called before use - call it at the top of every page.
\ contains information about uploaded files - always validate file type and size.
Never trust \ values directly - they can be manipulated by the client.

PHP Superglobals $_GET, $_POST, $_SESSION: Tutorial, Examples, FAQs & Interview Tips

$_GET and $_POST

$_SERVER

$_FILES, $_ENV, $_COOKIE, $_SESSION

Level Up Your Php Skills

Popular Tutorials

Ready to Level Up Your Skills?