How can PHP be used to extract data from a textarea in a form?

To extract data from a textarea in a form using PHP, you can access the value of the textarea by using the $_POST superglobal array. You need to make sure the form method is set to "post" and the textarea has a name attribute. Then, in your PHP script, you can retrieve the data by accessing $_POST['textarea_name'].

// HTML form
<form method="post">
    <textarea name="message"></textarea>
    <input type="submit" value="Submit">
</form>

// PHP script
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $message = $_POST['message'];
    echo "Message from textarea: " . $message;
}