Cannot send email using mail function - php

Question

First question and first time looking at PHP so please bear with me.
I currently have the below jQuery which is calling a php file:
$(document).on('click', '#btnContactUs', function () {
var name = $("input#name").val();
var email = $("input#email").val();
var subject = $("input#subject").val();
var message = $("input#message").val();
var dataString = 'name='+ name + '&email=' + email + '&subject=' + subject + '&message=' + message;
$.ajax({
type: "POST",
url: "php/message.php",
data: dataString,
success: function(response) { alert(response); }
});
return false;
});
The console is logging the call as successful (XHR finished loading: POST "php/message.php").
Below is the full script in the file:
<?php
$to = 'nobody#example.com';
$subject = 'the subject';
$message = 'hello';
$headers = 'From: webmaster#example.com' . "\r\n" .
'Reply-To: webmaster#example.com' . "\r\n" .
'X-Mailer: PHP/' . phpversion();
mail($to, $subject, $message, $headers);
?>
The email is not being sent/received (I am checking Spam also).
The files are hosted on a web server which has PHP installed. The alert box is popping up, but empty. The initial AJAX call is made from a submit button on a webpage.
EDIT: I am sending this to my personal email, which I have not included above.
EDIT: Even when visiting the URL of the script the email is still not being sent.
FINAL EDIT: The resolution is that my server did not have PHP mail installed - it is not supported as it is considered unreliable and therefore they recommend SMTP. To figure this out I used DrewT's solution of using SSH to check for "which sendmail"
Hope this scenario helps someone in the future.
Thanks all.

Answer 1

What seems to be happening is you are not sending your information in the correct format because you don't parse your var dataString on the server. I would try something like:
var name = $("input#name").val();
var email = $("input#email").val();
var subject = $("input#subject").val();
var message = $("input#message").val();
Then in your post function:
$.ajax({
type: "POST",
url: "php/message.php",
data : { name: name, email: email, subject: subject, message: message },
success: function (response, status, err) {
// do stuff...
// NOTE: don't return false or it won't send
// 'return false' only if the form is incomplete
// and you don't want the email sent out prematurely
}
});
Then to receive these vars in your PHP:
$name = $_POST['name'];
$email = $_POST['email'];
$subject = $_POST['subject'];
$message = $_POST['message'];
Now you can send an email like this:
// Enter your send email address
$to = 'email#example.com';
// Add your headers
$header = "from: $name <$email>";
// only send it if we have all the data we need
if( $subject !== "" || " " && $message !== "" || " " && $name !== "" || " " && $mail_from !== "" || " " ) {
$send_contact = mail($to,$subject,$message,$header);
// check if message was sent
// and provide some formatting (html) to send along in our response
if ($send_contact) {
echo '<div class="msg-sent">
Your message was sent successfully yay!
</div>';
}
else {
echo '<div class="msg-send-failed">
SEND FAILED :0
</div>';
}
}
else {
echo '<div class="msg-had-empty">
YOU HAD EMPTY POST VARIABLES :0
</div>';
}
Beyond that you will need to debug using the networks tab in your browser's inspector./ good luck!