Variables not populating from PHP Script to mail message [duplicate]

The script does run, and I get the email. None of the information in the variables appears in the message, though. I get the plain text (“Query from” in the subject and “From” in the body). I have pasted the PHP script and the HTML form below. I would love to use PHPMail, but I don’t know if it is in the hosting environment I use, and I cannot install it myself. Until I can find out, I am using the native mail() function. Thanks in advance.

PHP Code 
<?php $to = "[email protected]"; 
$subject = "Query from" . htmlspecialchars($_POST['customer']); 
$msgBody = htmlspecialchars($_POST['msgBody']) . " From: "; 
$from = htmlspecialchars($_POST['subAdd']); $message = $from . " " . $msgBody;

if (mail($to, $subject, $message)){
    header("Location: https://bkjdesignspa.com");
}
else{
     echo "<script>window.alert('There was a problem sending the message.')</script>";
}

?>

HTML form

<form id="contactInfo" method="post" action="contactForm.php">                 
    <label>Name</label><br>                 
    <input type="text" placeholder="Name" required><br>                 
    <label>Email</label><br>                 
    <input type="email" id="subAdd" placeholder="Email Address" required><br>                 
    <label>Details</label><br>                 
    <textarea id="msgBody" placeholder="Details of request" style="width: 10em; height: 5em;" required></textarea><br>                                <input type="submit" value="Submit">             
</form><br>