Skip to main content

⚙️ | Predefined Variables

https://www.php.net/manual/en/reserved.variables.php

https://www.php.net/manual/en/language.variables.scope.php

In PHP, some predefined variables are available at all times and facilitate the management of interactions between the server, the client, and the execution environment. Among these variables, we find superglobals and other specific variables.

Superglobals​

Superglobals are associative arrays that contain information related to the execution environment, HTTP requests, uploaded files, etc. They are accessible everywhere in the script, without the need to pass them as arguments.

$GLOBALS

Contains all global variables of the script.

$_SERVER

Information about the server and the environment (e.g., $_SERVER['HTTP_HOST'] for the host name).

$_GET

Contains data sent via an HTTP GET request (e.g., from a URL).

URL : http://example.com/page.php?name=toto&age=30

echo "Name: " . $_GET['name'];
echo "Age: " . $_GET['age'];
🖥️ Output
Name: toto
Age: 30
$_POST

Contains data sent via an HTTP POST request (e.g., from a form).

<form method="post" action="/process.php">
    <input type="text" name="first_name" placeholder="Your first name">
    <input type="submit" value="Send">
</form>
// Display the first name sent via the form
echo "First Name: " . $_POST['first_name'];
$_FILES

Contains files uploaded via a form.

<form action="/upload.php" method="post" enctype="multipart/form-data">
    <input type="file" name="my_file">
    <input type="submit" value="Upload">
</form>
// No error
if ($_FILES['my_file']['error'] === UPLOAD_ERR_OK) {
    $file_name = $_FILES['my_file']['name'];
    $temporary_name = $_FILES['my_file']['tmp_name'];
    move_uploaded_file($temporary_name, "uploads/$file_name");
}
// One or more errors
else {
    echo "Error during upload.";
}

See the list of file upload errors.

$_COOKIE

Contains the cookies sent by the client.

setcookie('user', 'toto', time() + 3600);

if (isset($_COOKIE['user'])) {
    echo 'User: ' . $_COOKIE['user'];
}
🖥️ Output
User: toto
$_SESSION

Sessions allow storing user information across different pages.

  • session_start(): Must be called to initialize the session.
  • session_destroy(): Used to destroy all session variables.

Example:

// Start the session
session_start();

// Store data in the session
$_SESSION['user'] = 'toto';

// Access the data
echo "User: " . $_SESSION['user'];

// Destroy the session
session_destroy();
🖥️ Output
User: toto
$_REQUEST

Combines data from $_GET, $_POST, and $_COOKIE.

$_ENV

Contains server environment variables.

echo $_ENV['HOME'];
🖥️ Output
/home/toto

Other predefined variables​

$argc

Contains the number of arguments passed to the script via the command line (similar to C).

$argv

Contains an array of arguments passed via the command line (similar to C).

X

Graph View