What is the difference between submitting a form using GET and POST methods in PHP?

When submitting a form using the GET method in PHP, the form data is appended to the URL, making it visible in the browser's address bar. This method is suitable for retrieving data from the server and bookmarking URLs. On the other hand, when using the POST method, the form data is sent in the HTTP request body, making it more secure as it is not visible in the URL. This method is ideal for submitting sensitive information like passwords.

<form action="process_form.php" method="post">
  <input type="text" name="username">
  <input type="password" name="password">
  <button type="submit">Submit</button>
</form>