Bootstrap v4 form red error border - php

Question

I'm just experimenting with the contact form of Bootstrap v4 and some PHP validation, but struggling to the red error border.
When the email input is not correct, a red border comes around with a text-balloon and with a red error message underneath it. That's just what I want. But this doesn't happen at the Name input. I just don't see where it goes wrong. I checked all the classes, but they're all identical.
Can someone help?
I know only name and email have !preg_match so far.
<?php
if (isset($_POST["submit"])) {
$name = $_POST['name'];
$email = $_POST['email'];
$message = $_POST['message'];
$human = intval($_POST['human']);
$from = 'Demo Contact Form';
$to = 'example#bootstrapbay.com';
$subject = 'Message from Contact Demo ';
$body = "From: $name\n E-Mail: $email\n Message:\n $message";
// Check if name has been entered
if (!preg_match("/^[a-zA-Z]+[a-zA-Z[:space:]]{2,}$/", $_POST['name'])) {
$errName = 'Please enter your name';
}
// Check if email has been entered and is valid
if (!preg_match("/^([a-zA-Z0-9])+([\.a-zA-Z0-9_-])*#([a-zA-Z0-9_-])+(\.[a-zA-Z0-9_-]+)*\.([a-zA-Z]{2,6})$/", $_POST['email'])) {
$errEmail = 'Please enter a valid email address';
}
//Check if message has been entered
if (!$_POST['message']) {
$errMessage = 'Please enter your message';
}
//Check if simple anti-bot test is correct
if ($human !== 5) {
$errHuman = 'Your anti-spam is incorrect';
}
// If there are no errors, send the email
if (!$errName && !$errEmail && !$errMessage && !$errHuman) {
if (mail ($to, $subject, $body, $from)) {
$result='<div class="alert alert-success">Thank You! I will be in touch</div>';
} else {
$result='<div class="alert alert-danger">Sorry there was an error sending your message. Please try again later</div>';
}
}
}
?>
<form class="form-horizontal" role="form" method="post" action="contact_test.php">
<div class="form-group">
<label for="name" class="col-sm-2 control-label">Name</label>
<div class="col-sm-10">
<input type="text" class="form-control" id="name" name="name" placeholder="First & Last Name" value="<?php echo htmlspecialchars($_POST['name']); ?>">
<?php echo "<p class='text-danger'>$errName</p>";?>
</div>
</div>
<div class="form-group">
<label for="email" class="col-sm-2 control-label">Email</label>
<div class="col-sm-10">
<input type="email" class="form-control" id="email" name="email" placeholder="example#domain.com" value="<?php echo htmlspecialchars($_POST['email']); ?>">
<?php echo "<p class='text-danger'>$errEmail</p>";?>
</div>
</div>
<div class="form-group">
<label for="message" class="col-sm-2 control-label">Message</label>
<div class="col-sm-10">
<textarea class="form-control" rows="4" name="message"><?php echo htmlspecialchars($_POST['message']);?></textarea>
<?php echo "<p class='text-danger'>$errMessage</p>";?>
</div>
</div>
<div class="form-group">
<label for="human" class="col-sm-2 control-label">2 + 3 = ?</label>
<div class="col-sm-10">
<input type="text" class="form-control" id="human" name="human" placeholder="Your Answer">
<?php echo "<p class='text-danger'>$errHuman</p>";?>
</div>
</div>
<div class="form-group">
<div class="col-sm-10 col-sm-offset-2">
<input id="submit" name="submit" type="submit" value="Send" class="btn btn-primary">
</div>
</div>
<div class="form-group">
<div class="col-sm-10 col-sm-offset-2">
<?php echo $result; ?>
</div>
</div>
</form>