我该如何正确构建这个PHP邮件脚本？

I am attempting to send the collected value's of a html form as an email to myself via PHP & Ajax. For some reason, I am able to update the UI with a success alert, however there's no actual email sent when I check my inbox. I am under the impression that my PHP script may be ill-structured, because when I log the results of my js function, all of the form values have been correctly captured.

Here is the JS:

function _(id){ return document.getElementById(id); };
function submitForm(){
    var formdata = new FormData();
    formdata.append( "first-name", _("first-name").value );
    formdata.append( "last-name", _("last-name").value );
    formdata.append( "email", _("email").value );
  formdata.append( "subject", _("subject").value );
  formdata.append( "message", _("message").value );
    var ajax = new XMLHttpRequest();
    ajax.open( "POST", "email_me.php" );
    ajax.onreadystatechange = function() {
        if(ajax.readyState == 4 && ajax.status == 200) {
            if(ajax.responseText == "success"){
                alert("Hey! It Worked!!");
            } else {
            // display error
            }
        }
    }
    ajax.send( formdata );
  // Display the key/value pairs
  for (var pair of formdata.entries()) {
      console.log(pair[0]+ ', ' + pair[1]);
  }
}

And Here is the php script (email_me.php file)

<?php
  if(isset($_POST['first-name'], $_POST['last-name'], $_POST['email'], $_POST['subject'], $_POST['message'])){
    $name = $_POST['first-name'];
    $email = $_POST['email'];
    $m = nl2br($_POST['message']);
    $to = "me@gmail.com";
    $from = $email;
    $subject = $_POST['subject'];
    $message = '<p>'.$m.'</p>';
    $headers = "From: $from
";
    $headers .= "MIME-Version: 1.0
";
    $headers .= "Content-type: text/html; charset=iso-8859-1
";
    if( mail($to, $subject, $message, $headers) ){
        echo "success";
    } else {
        echo "The server failed to send the message. Please try again later.";
    }
  }
?>

What seem's to be the issue? Im running the current version of Apache with a localhost, using MAMP Pro btw.

Here are the server logs:

Marker - Aug 23, 2016, 12:34:32 PM

Aug 23 12:35:24 MacBookAir postfix/master[7884]: daemon started -- version 2.11.0, configuration /etc/postfix Aug 23 12:36:24 MacBookAir postfix/master[7884]: master exit time has arrived

Aug 23 12:36:24 MacBookAir postfix/master[7885]: daemon started -- version 2.11.0, configuration /etc/postfix Aug 23 12:37:24 MacBookAir postfix/master[7885]: master exit time has arrived Aug 23 12:37:24 MacBookAir r postfix/master[7886]: daemon started -- version 2.11.0, configuration /etc/postfix

update you php code and check it will work

 if(isset($_POST['first-name'], $_POST['last-name'], $_POST['email'], $_POST['subject'], $_POST['message'])){
    $name = $_POST['first-name'];
    $email = $_POST['email'];
    $m = nl2br($_POST['message']);
    $message = '<p>Name => '.$name.' <br/> Email =>'.$email.'<br /> Message =>'.$m.'</p>';
    $to = "me@gmail.com";

    $subject = $_POST['subject'];
    $headers = "From: noreply@something.com
"; // use 

    $headers .= "MIME-Version: 1.0
";
    $headers .= "Content-type: text/html; charset=iso-8859-1
";  // use 

    $headers.= "X-Priority: 1
";
    if( mail($to, $subject, $message, $headers) ){
        echo "success";
    } else {
        echo "The server failed to send the message. Please try again later.";
    }
  }