PHP - examples - 09 : forms

code:
            <form method="POST" action="/tutorials/PHP/PHP-examples/PHP-examples-09.php" accept-charset="UTF-8">
                    <p><label>your ame<strong>*</strong><br>
                        <input type="text" size="48" name="name" value="<?php if(isset($_POST['name'])) echo htmlspecialchars
                        ($_POST['name']);?>">
                    </label></p>
                    <p><label>email address<strong>*</strong><br>
                        <input type="email" size="48" name="email" value="<?php if(isset($_POST['email'])) echo htmlspecialchars
                        ($_POST['email']);?>">
                    </label></p>
                    <p><label>subject<br>
                        <input type="text" size="48" name="subject" value="<?php if(isset($_POST['subject'])) echo htmlspecialchars
                        ($_POST['subject']); ?>">
                    </label></p>
                    <p><label>enquiry<strong>*</strong><br>
                        <textarea name="message" cols="48" rows="8"><?php if(isset($_POST['message'])) echo htmlspecialchars
                        ($_POST['message']); ?></textarea>
                    </label></p>
                    <p><input type="submit" name="sendfeedback" value="Send Message"></p>
                </form>
                <?php 
                // form handler
                if($_POST && isset($_POST['sendfeedback'], $_POST['name'], $_POST['email'], $_POST['subject'], $_POST['message'])) {
                        $name = $_POST['name'];
                        $email = $_POST['email'];
                        $subject = $_POST['subject'];
                        $message = $_POST['message'];
                
                        if(!$name) {
                            $errorMsg = "Please enter your Name";
                        } elseif(!$email || !preg_match("/^\S+@\S+$/", $email)) {
                            $errorMsg = "Please enter a valid Email address";
                        } elseif(!$message) {
                            $errorMsg = "Please enter your comment in the Message box";
                        } else {
                            // send email and redirect
                            $to = "feedback@example.com";
                            if(!$subject) $subject = "Contact from website";
                            $headers = "From: webmaster@example.com" . "\r\n";
                            mail($to, $subject, $message, $headers);
                            header("Location: http://www.example.com/thankyou.html");
                            exit;
                        }
                    }
                ?>