Ajax错误:加载资源失败:服务器响应状态为500(内部服务器错误)

我试图使一个ajax功能，允许我的网站发送消息给我，而不刷新页面。但我做不到因为每次点击它，控制台都会出现这个错误:

加载资源失败:服务器响应状态为500(内部服务器错误)。

$(function() {
var form = $('#ajax-contact');
var formMessages = $('#form-messages');

$(form).submit(function(event) {
    event.preventDefault();
    var formData = $(form).serialize();
    $.ajax({
        type: 'POST',
        url: $(form).attr('action'),
        data: formData
    }).done(function(response) {
        // Make sure that the formMessages div has the 'success' class.
        $(formMessages).removeClass('error');
        $(formMessages).addClass('success');
        // Set the message text.
        $(formMessages).text(response);
        // Clear the form.
        $('#name').val('');
        $('#email').val('');
        $('#message').val('');
    }).fail(function(data) {
        // Make sure that the formMessages div has the 'error' class.
        $(formMessages).removeClass('success');
        $(formMessages).addClass('error');
        // Set the message text.
        if (data.responseText !== '') {
            $(formMessages).text(data.responseText);
        } else {
            $(formMessages).text('Oops! An error occured and your message could not be sent.');
        }
    });
});

});

<?php
// Only process POST reqeusts.
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // Get the form fields and remove whitespace.
    $name = strip_tags(trim($_POST["name"]));
            $name = str_replace(array("'r","'n"),array(" "," "),$name);
    $email = filter_var(trim($_POST["email"]), FILTER_SANITIZE_EMAIL);
    $message = trim($_POST["message"]);
    // Check that data was sent to the mailer.
    if ( empty($name) OR empty($message) OR !filter_var($email, FILTER_VALIDATE_EMAIL)) {
        // Set a 400 (bad request) response code and exit.
        http_response_code(400);
        echo "All fields must be filled.";
        exit;
    }
    // Set the recipient email address.
    // FIXME: Update this to your desired email address.
    $recipient = "example@example.com";
    // Set the email subject.
    $subject = "New Message from $name";
    // Build the email content.
    $email_content = "Name: $name'n";
    $email_content .= "Email: $email'n'n";
    $email_content .= "Message:'n$message'n";
    // Build the email headers.
    $email_headers = "From: $name <$email>";
    // Send the email.
    if (mail($recipient, $subject, $email_content, $email_headers)) {
        // Set a 200 (okay) response code.
        http_response_code(200);
        echo "Thank You! Your message has been sent.";
    } else {
        // Set a 500 (internal server error) response code.
        http_response_code(500);
        echo "Something went wrong.";
    }
} else {
    // Not a POST request, set a 403 (forbidden) response code.
    http_response_code(403);
    echo "There was a problem with your submission, please try again.";
}
?>