What are the differences between using POST and GET methods in PHP forms, and when should each method be used?

When submitting a form in PHP, the main differences between using POST and GET methods are how the data is sent. POST sends data in the HTTP request body, while GET sends data in the URL. POST is more secure as it doesn't expose sensitive information in the URL, while GET is useful for retrieving data and bookmarking URLs. POST should be used for forms that involve sensitive information like passwords, while GET can be used for simple data retrieval.

<form method="post" action="process.php">
    <label for="username">Username:</label>
    <input type="text" id="username" name="username">
    
    <label for="password">Password:</label>
    <input type="password" id="password" name="password">
    
    <button type="submit">Submit</button>
</form>