Built-In Superglobal Variables in PHP
Superglobal variables in PHP are built-in variables that are always accessible, regardless of the scope (inside or outside of functions). They are automatically populated and can be used to collect data from forms, sessions, cookies, URLs, and the server itself.
$_GET[]
- Collects data sent via the URL using a query string (e.g., after the “?” in a URL.
// URL: example.com?name=John
$name = $_GET['name']; // "John"- Use case: Sending data via URL for actions like search queries or passing parameters between pages.
$_POST[]
- Collects data sent via an HTML form using the POST method.
// Assuming a form field with name="username"
$username = $_POST['username']; // "JohnDoe"- Use case: Securely sending sensitive data like login credentials, as POST doesn’t append data to the URL.
$_REQUEST[]
- Can collect data from both GET and POST methods.
$search = $_REQUEST['search']; // Works for both GET and POST- Use case: Flexible data retrieval, allowing you to fetch data regardless of whether it was sent via GET or POST.
$_FILES[]
- Handles file uploads in forms
$file = $_FILES['fileToUpload']['name'];GET vs POST?
| Feature | GET | POST |
|---|---|---|
| Data Visibility | Appends data to the URL and is visible | Data is sent in the request body and is hidden |
| Data Length | Limited by URL length (typically 2048 characters) | No restrictions on data length (large data can be sent) |
| Use Case | Used for retrieving data (e.g., search queries) | Used for sending sensitive data (e.g., forms, file uploads) |
| Browser History | Data is saved in browser history | Data is not saved in browser history |
| Bookmarkable | Can be bookmarked | Cannot be bookmarked |
| Security | Less secure (data visible in URL) | More secure (data is not visible in the URL) |
| Data Resubmission | Can be resubmitted (via refresh) | Cannot be easily resubmitted without a warning |
| Caching | Cached by browsers | Not cached by browsers |
Handling Form Data Exercise 01
Create a HTML page with a hyperlink to send the following data to the server. Create a PHP page to access this data.
<a href="./data.php?userid=4&username=neo&status=true">Send data to server</a>
<!-- index.html --><?php
echo "User ID : ", $_GET['userid'],"<br>";
echo "Username : ", $_GET['username'],"<br>";
echo "Status : ", $_GET['status'],"<br>";
?>
// data.php