Introduction to superglobals

Superglobals are built-in arrays available in every scope: $_GET, $_POST, $_SERVER, $_SESSION, $_COOKIE, $_FILES, $_ENV. They mirror HTTP input and server metadata.

Common superglobals

• $_GET — query string parameters (?page=2)
• $_POST — form body fields (application/x-www-form-urlencoded or multipart)
• $_SERVER — request method, URI, headers (as HTTP_* keys)
• $_SESSION — server-side session bag after session_start()

Playground simulation

The runner may not populate real superglobals. Treat sample arrays as stand-ins—the access pattern is identical:

$_GET = ['id' => '5']; // simulated
$id = (int) ($_GET['id'] ?? 0);

Security mindset

Never trust superglobal values. Validate, cast, and use prepared statements for database work. Escape on output.

Important interview questions and answers

1. Q: GET vs POST superglobals?
   A: $_GET from query string; $_POST from request body—method choice affects caching, bookmarks, and size limits.
2. Q: Why are they called superglobals?
   A: They are always available without global

Self-check

1. Which superglobal holds REQUEST_METHOD?
2. Why cast $_GET['id'] to int?

Tip: Treat every superglobal value as untrusted—validate, cast, and never concatenate raw input into SQL.