$valid = true;
$errors = array();

$contact = array(
    'name' => null,
    'email' => null,
    'message' => null

// Check if the form has been posted
if (isset($_POST['name'], $_POST['email'], $_POST['message'])) {
    $contact = filter_input_array(INPUT_POST, array(
        'name'   => FILTER_SANITIZE_STRING,
        'email'   => FILTER_SANITIZE_STRING,
        'message'   => FILTER_SANITIZE_STRING,
    ), true);
    if (empty($contact['name'])) {
        $valid = false;
        $errors['name'] = "You must enter your name.";
    if (empty($contact['email'])) {
        $valid = false;
        $errors['email'] = "You must enter your email address.";
    } elseif (!filter_input(INPUT_POST, 'email', FILTER_VALIDATE_EMAIL)) {
        $valid = false;
        $errors['email'] = "You must enter a valid email address.";
    if (empty($contact['message'])) {
        $valid = false;
        $errors['message'] = "You must enter a message.";
    if ($valid) {
        // The email address the email will be sent to
        $to = "";
        // The email subject
        $subject = "Contact Form Submission";
        // Set the from and reply-to address for the email
        $headers = "From:\r\n"
                 . "Reply-To: " . $contact['email'] . "\r\n"
                 . "X-Mailer: PHP/" . phpversion();
        // Build the body of the email
        $mailbody = "The contact form has been filled out.\n\n"
                  . "Name: " . $contact['name'] . "\n"
                  . "Email: " . $contact['email'] . "\n"
                  . "Message:\n" . $contact['message'];
        // Send the email
        mail($to, $subject, $mailbody, $headers);
        // Go to the thank you page
        header("location: thankyou.html");

<!DOCTYPE html>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <title>Contact Us</title>
    <link rel="stylesheet" href="styles.css">
    <form action="contact.php" method="post" accept-charset="utf-8">
            <legend>Contact Us</legend>
            <?php if (!$valid): ?>
                <div class="error">
                    <?php foreach($errors as $message):?>
                        <div><?php echo htmlspecialchars($message); ?></div>
                    <?php endforeach; ?>
            <?php endif; ?>
            <div class="row">
                <label for="name">Name: </label>
                <input id="name" type="text" name="name" value="<?php echo htmlspecialchars($contact['name']);?>">
            <div class="row">
                <label for="email">Email Address: </label>
                <input id="email" type="text" name="email" value="<?php echo htmlspecialchars($contact['email']);?>">
            <div class="row">
                <label for="message">Message:</label>
                <textarea id="message" name="message"><?php echo htmlspecialchars($contact['message']);?></textarea>
            <div class="row">
                <input type="submit" value="Submit">
downloadDownload PNG downloadDownload JPEG downloadDownload SVG

Tip: You can change the style, width & colours of the snippet with the inspect tool before clicking Download!

Click to optimize width for Twitter