PHP form processor not working - php

Question

I just started learning php not long ago, and I am currently building a "contact us" form which will send the user input to my email. I have been on this for days thinking I will figure it out, but I am not getting it. I wanna also be able to receive the user's input in my email and also be able to detect the user's IP address. When I submitted the form, I received every other input but the IP address though I used "localhost".
I tried with the <input type="hidden" name="message" value="<?php echo $_SERVER['REMOTE_ADDR']; ?>"> but I read online that it's better to do it without the <input type="hidden"> and just process everything in the form processor script. Please kindly help me with this.
<?php
$emailError = "";
$messageError = "";
function getUserIp(){
$client = $_SERVER['HTTP_CLIENT_IP'];
$forward = $_SERVER['HTTP_X_FORWARD_FOR'];
$remote = $_SERVER['REMOTE_ADDR'];
if(filter_var($client, FILTER_VALIDATE_IP)) {
$ip = $client;
}elseif(filter_var($forward, FILTER_VALIDATE_IP)) {
$ip = $client;
}else{
$ip = $remote;
}
return $ip;
}
if(isset($_POST['submit'])){
//declares variable
$email = $_POST["email"];
$subject = $_POST["subject"];
$message = $_POST["message"];
if(empty($_POST['email'])){
$emailError = "Please enter your email";
}
if(empty($_POST['subject'])){
$subjectError = "Please enter a subject?";
}
}
if(!empty($_POST['email']) && !empty($_POST['subject'])){
// Send the email
$to = "you#yourdomain.com";
$email = "From: $email";
$subject = "Subject: $subject";
$message = "$message" . "\n\n\n==- Sent from the website with IP Address: " . $ip . " -==";;
$headers = "From: $email,";
$send_contact=mail($to,$email,$subject,$message,$headers);
header("Location: domain");
}
?>

Answer 1

change below section --
if(!empty($_POST['email']) && !empty($_POST['subject'])){
// Send the email
$to = "you#yourdomain.com";
$ip =getUserIp();
$email = "From: $email";
$subject = "Subject: $subject";
$message = "$message" . "\n\n\n==- Sent from the website with IP Address: " . $ip . " -==";;
$headers = "From: $email,";
$send_contact=mail($to,$email,$subject,$message,$headers);
header("Location: domain");
}