我的$.post函数没有'；t返回任何数据

我是Php和Ajax的新手，我一直在思考这个问题。我正试图使用$.post简写函数用ajax更新我的简单表单，但我的脚本没有返回任何内容。我也尝试过$.ajax，并使用了不同的数据类型，如json对象、json变量、serialize()。。等

HTML

    <section class="contact" id="contact">

  <h2>Do you have a project in mind? Let's discuss it</h2>
    <div id="form-messages">
    </div>

   <form action="" method="post" id="contact-form">
        <div class="row">
            <div class="col span-1-of-4"><label for="name">Your name</label></div>
            <div class="col span-3-of-4"><input type="text" name="name" id="name" placeholder="Enter your name ..."></div>
        </div>
        <div class="row">
            <div class="col span-1-of-4"><label for="email">Your email</label></div>
            <div class="col span-3-of-4"><input type="email" name="email" id="email" placeholder="Enter your email ..."></div>
        </div>
        <div class="row">
            <div class="col span-1-of-4"><label for="message">Your message</label></div>
            <div class="col span-3-of-4"><textarea name="message" id="message" placeholder="Type in your message ..."></textarea></div>
        </div>
        <div class="row">
        <div class="col span-1-of-4"></div>
            <div class="col span-3-of-4"><input type="submit" name="submit" id="submit" value="Send your message"></div>
        </div>
    </form>


</section>

PHP

<?php           
$name= $_POST['name'];
$email= $_POST['email'];
$message= $_POST['message'];
$error="";
$result="";
if (isset($_POST["submit"])) {
if (!$name) {
    $error="<br />Please enter your name";
}
if (!$email) {
    $error.="<br />Please enter your email address";
}
if (!$message) {
    $error.="<br />Please enter a message";
}
if ($_POST['email']!="" AND !filter_var($_POST['email'], FILTER_VALIDATE_EMAIL)) {
        $error.="<br />Please enter a valid email address";
    }                       
if ($error) {
    $result='<div class="error-message"><p id="alert"><strong>There were error(s) in your form:</strong>'.$error.'</p></div>';
} else {
    if (mail("abderrahim.gadmy@gmail.com", "Gadmy Visions: Someone sent you a message!", 
    "Name: ". $_POST['name']."
    Email: ".$_POST['email']."
    Comment: ".$_POST['message'])) {
        $result='<div class="success-message"><p id="alert"><strong>Thank you!</strong> I''ll be in touch</p></div>';
    } else {                                                 
        $result='<div class="error-message"><p id="alert">Sorry, there was an error sending your message. Please try again later.</p></div>';
    }
}
 echo $result;
}
?>

JS-

$(document).ready(function(){
            $('#contact-form').on('submit',function(event){

    $.post('contact.php',$('form').serialize(), function(data){
        $('#form-messages').html(data);        
    });
    //Prevent refresh
    event.preventDefault();      
    });
});