PHP Superglobals

Superglobals are built-in PHP variables that can be accessed from anywhere in your program.

Unlike normal variables, they do not require:

global

They are automatically available.

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List of Superglobals

Variable	Description
$_GET	URL Parameters
$_POST	Form Data
$_REQUEST	GET + POST + COOKIE
$_SERVER	Server Information
$_FILES	Uploaded Files
$_COOKIE	Browser Cookies
$_SESSION	User Sessions
$_ENV	Environment Variables
$GLOBALS	Global Variables

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$_GET

Retrieves data from URL.

Example:

https://example.com/index.php?id=10

PHP:

$id = $_GET["id"];

Output:

10

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Checking Values Safely

Never do:

$id = $_GET["id"];

Because it may not exist.

Better:

$id =
$_GET["id"]
?? null;

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Multiple Parameters

?name=Aayan&rank=Owner

PHP:

$name =
$_GET["name"];

$rank =
$_GET["rank"];

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$_POST

Used in forms.

<form method="POST">

Example:

$username =
$_POST["username"];

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Why POST?

POST data:

✅ Hidden from URL

✅ Supports large data

✅ Used for authentication

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Example Login System

if (
    isset($_POST["login"])
) {

    $username =
        $_POST["username"];

    $password =
        $_POST["password"];

}

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$_REQUEST

Contains:

GET
POST
COOKIE

Example:

$name =
$_REQUEST["name"];

Usually avoid using this because it becomes unclear where data comes from.

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$_SERVER

One of the most useful superglobals.

Contains:

• IP Address
• Request Method
• Host
• PHP Version
• User Agent
• Paths

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Request Method

$_SERVER["REQUEST_METHOD"]

Output:

GET
POST

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User Agent

$_SERVER["HTTP_USER_AGENT"]

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IP Address

$_SERVER["REMOTE_ADDR"]

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Current File

$_SERVER["PHP_SELF"]

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Server Name

$_SERVER["SERVER_NAME"]

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Request URI

$_SERVER["REQUEST_URI"]

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Example API Router

$method =
$_SERVER["REQUEST_METHOD"];

switch ($method) {

    case "GET":
        break;

    case "POST":
        break;
}

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$_FILES

Used for file uploads.

HTML:

<input type="file">

PHP:

$_FILES["image"];

Structure:

[
    "name",
    "tmp_name",
    "size",
    "error",
    "type"
]

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Upload Example

move_uploaded_file(
    $_FILES["image"]["tmp_name"],
    "uploads/image.png"
);

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Security

Always validate:

mime_content_type()

Never trust file extensions.

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$_COOKIE

Stores browser information.

Create:

setcookie(
    "username",
    "Aayan"
);

Read:

$_COOKIE["username"];

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$_SESSION

Sessions store data on server.

Start session:

session_start();

Store:

$_SESSION["user"] =
"Aayan";

Read:

echo
$_SESSION["user"];

Destroy:

session_destroy();

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Login Example

$_SESSION["logged"] =
true;

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$_ENV

Environment Variables.

Example:

DB_HOST=127.0.0.1
DB_PASSWORD=secret

PHP:

$_ENV["DB_HOST"];

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$GLOBALS

Contains every global variable.

Example:

$name = "Aayan";

echo
$GLOBALS["name"];

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Security Best Practices

Never trust:

$_GET
$_POST
$_FILES

Always validate and sanitize.

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Useful Functions

htmlspecialchars()
filter_var()
trim()

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Exercises

1. Create login form.
2. Read GET parameters.
3. Upload image.
4. Store user session.

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Real World Usage

Superglobals are used in:

• Laravel
• APIs
• CMS
• Authentication Systems
• Dashboards
• PocketMine Web Panels
• ZyroNetwork Panels

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Next Chapter

➡ File Handling