PHP Validate Form and send Mail

<?php
if(isset($_POST['sendmail'])){
$name = $_POST['name'];
$email = $_POST['email'];
$website = $_POST['website'];
$subject = $_POST['subject'];
$message = $_POST['message'];
$to = "example@yahoo.com";               // << write your own email here

$error = false;

//validate name

if (empty($name)) {
    $nameErr = "<div class='errors'>Name must be filled.</div>";
}else if(!preg_match("/^[a-zA-Z ]*$/", $name)){
    $nameErr = "<div class='errors'>Only letters and white space allowed.</div>";
}else{
    $valid_name = true;
}

//validate email

if(empty($email)){
    $mailErr = "<div class='errors'>Email can not be empty.</div>";
}else if(!(preg_match("/^[a-zA-Z0-9\-_]+(\.[a-zA-Z0-9\-_]+)*@[a-z0-9]+(\-[a-z0-9]+)*(\.[a-z0-9]+(\-[a-z0-9]+)*)*\.[a-z]{2,4}$/", $email))){
    $mailErr = "<div class='errors'>Please input a valid email address.</div>";
}else{
    $valid_email = true;
}

//validate subject

if (empty($subject)) {
    $subjectErr = "<div class='errors'>Please write your mail subject.</div>";
}else if (!preg_match("/^[a-zA-Z. ]*$/", $subject)) {
    $subjectErr = "<div class='errors'>Only letters and white space allowed.</div>";
}else{
    $valid_subject = true;
}

//validate message
if (empty($message)) {
    $messageErr = "<div class='errors'>Message can not be empty.</div>";
}else{
    $valid_message = true;
}

//if all validation are true then send mail

if ($valid_email && $valid_message && $valid_name && $valid_subject) {
    $send_mail = @mail($to,$subject,$message,"From: $name  <$email>");
}

//Show success of fail message

if($send_mail){
    $successMsg = "<div class='done'>Email has been sent.</strong></div>";
}else{
    $successMsg = "<div class='done'>Something is wrong.</strong></div>";
}

}


?>
<!DOCTYPE HTML>
<html lang="en-US">
<head>
    <meta charset="UTF-8">
    <title>Contact Page</title>
    <link rel="stylesheet" type="text/css" href="style.css" media="all" />
</head>
<body>
    <div class="container">
        <div class="contactform">
            <form class="form" action="index.php" method="post" name="contactus">
            <?php echo $successMsg; ?>
                <fieldset>
                    <legend>Your Info</legend>
                    <label>Name*</label><input name="name" type="text" size="45" placeholder="Your Full Name" /><?php echo $nameErr; ?><br />
                    <label>Email*</label><input name="email" type="email" size="45" placeholder="youremail@example.com" /><?php echo $mailErr; ?><br />
                    <label>Website</label><input name="website" type="text" size="45" placeholder="www.example.com" /><br />
                </fieldset>
                <fieldset>
                    <legend>Your Message</legend>
                    <label>Subject*</label><input name="subject" type="text" size="45" placeholder="Subject of your massage." /><?php echo $subjectErr; ?><br />
                    <label>Message*</label><textarea name="message" cols="35" rows="7" placeholder="Write your massage here..."></textarea><?php echo $messageErr; ?>
                </fieldset>
                    <input name="sendmail" class="submit" type="submit" value="Send Email" />
            </form>
        </div>
    </div>
</body>
</html>