What are the differences between using GET and POST methods for form data submission in PHP?

When submitting form data in PHP, the main differences between using GET and POST methods lie in how the data is sent. GET method appends the form data to the URL, making it visible in the address bar and limited in the amount of data that can be sent. POST method sends the form data in the request body, making it more secure and suitable for sending larger amounts of data.

// Using POST method for form data submission
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // Access form data using $_POST superglobal
    $username = $_POST['username'];
    $password = $_POST['password'];
    
    // Process form data
    // ...
}