simple php mail snippet with PHPMailer through SMTP and Google reCAPTCHA

contact-form.js

var form = $('#form');

form.find('[type="submit"]').on('click', function(e) {
        
    var isFormValid = form[0].checkValidity();
    var isCaptchaOk = $('#g-recaptcha-response').val();
    
    if(isFormValid && isCaptchaOk) {
        e.preventDefault();
        var dataObj = {
            name:  $.trim(form.find('input[name="name"]').val()),
            email:  $.trim(form.find('input[name="email"]').val()),
            message:  $.trim(form.find('textarea').val()),
            captcha : grecaptcha.getResponse()
        };
         
        $(this).addClass('disabled');
        form.find('.error-captcha').remove();
        
        ajaxSend(dataObj);
        
    } else if(!isCaptchaOk) {
        if(isFormValid) e.preventDefault();
        if(form.find('.error-captcha').length == 0) {
            form.find('.g-recaptcha').parent().append('<span class="error-captcha">Please fill up the captcha.</span>');
        }
    } else if(isCaptchaOk) {
        if(isFormValid) e.preventDefault();
        form.find('.error-captcha').remove();
    }
});


var ajaxSend = function(dataObj) {
    $.ajax({
        type: 'POST',
        url: 'send.php',
        data: dataObj,
        statusCode: {
            200: function () {
                toastr['success']('Message sent successfully.'); //I use toastr https://github.com/CodeSeven/toastr
                form.find('input:not([type="submit"]), textarea').val('');
                form.find('input:checkbox').attr('checked', false); 
            },
            400: function() { toastr['error']('400 Client Error.'); },
            403: function() { toastr['error']('403 Bad Request.'); },
            404: function() { toastr['error']('404 Not Found.'); },
            500: function() { toastr['error']('500 Server Error.'); }
        }, 
        complete: function() {
            form.find('[type="submit"]').removeClass('disabled');
        }
    });
};

send.php

<?php
    require 'PHPMailer/PHPMailerAutoload.php';

    if ($_SERVER["REQUEST_METHOD"] != "POST") {
        http_response_code(403); // header(':', true, 403); if php version < 5.4
        echo "403 Forbidden";
        exit; 
    }

    if (!isset($_POST["email"]) || !isset($_POST["message"])) {
        http_response_code(400); // header(':', true, 400); if php version < 5.4
        echo "400 Client Error";
        exit;
    }


    if(!isset($_POST["captcha"]) || !($captcha=$_POST["captcha"])) {
        http_response_code(400); // header(':', true, 400); if php version < 5.4
        echo "400 Bad Captcha";
        exit;
    }

    $secret = "YOUR SECRET";
    $response = json_decode(file_get_contents("https://www.google.com/recaptcha/api/siteverify?secret=".$secret."&response=".$captcha."&remoteip=".$_SERVER["REMOTE_ADDR"]), true);

    if(!isset($response["success"]) || !$response["success"]) {
        http_response_code(400); // header(':', true, 400); if php version < 5.4
        echo "400 Client Error";
        exit;
    }

    $mail = new PHPMailer;

    $mail->isSMTP();
    $mail->Host = 'smtp1.example.com';
    $mail->SMTPAuth = true;
    $mail->Username = '[email protected]';
    $mail->Password = 'password';
    $mail->SMTPSecure = 'ssl';
    $mail->Port = 465;

    $mail->setFrom('[email protected]', 'Contact Form Site.com');
    $mail->addReplyTo($_POST["email"], $_POST['name']);
    $mail->addAddress('[email protected]');
    $mail->isHTML(true);


    $mail->Subject = 'Contact form message from the website';
    $mail->Body    = 'Name: ' . $_POST['name'] . '<br /><br />' . 'Message:' . '<br />' . $_POST['message'];
    $mail->AltBody = 'Name: ' . $_POST['name'] . 'Message: ' . $_POST['message'];

    if(!$mail->send()) {
        header(':', true, 500);
        echo '500 Server Error: ' . $mail->ErrorInfo;
        exit;
    } 

    header(':', true, 200);
    echo 'Message sent successfully';
    exit;