Bootstrap Modal Popup Form Submit with Ajax & PHP

<!-- Latest minified bootstrap css -->
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">

<!-- jQuery library -->
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.0/jquery.min.js"></script>

<!-- Latest minified bootstrap js -->
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>

<!-- Button to trigger modal -->
<button class="btn btn-success btn-lg" data-toggle="modal" data-target="#modalForm">
    Open Contact Form
</button>

<!-- Modal -->
<div class="modal fade" id="modalForm" role="dialog">
    <div class="modal-dialog">
        <div class="modal-content">
            <!-- Modal Header -->
            <div class="modal-header">
                <button type="button" class="close" data-dismiss="modal">
                    <span aria-hidden="true">&times;</span>
                    <span class="sr-only">Close</span>
                </button>
                <h4 class="modal-title" id="myModalLabel">Contact Form</h4>
            </div>
            
            <!-- Modal Body -->
            <div class="modal-body">
                <p class="statusMsg"></p>
                <form role="form">
                    <div class="form-group">
                        <label for="inputName">Name</label>
                        <input type="text" class="form-control" id="inputName" placeholder="Enter your name"/>
                    </div>
                    <div class="form-group">
                        <label for="inputEmail">Email</label>
                        <input type="email" class="form-control" id="inputEmail" placeholder="Enter your email"/>
                    </div>
                    <div class="form-group">
                        <label for="inputMessage">Message</label>
                        <textarea class="form-control" id="inputMessage" placeholder="Enter your message"></textarea>
                    </div>
                </form>
            </div>
            
            <!-- Modal Footer -->
            <div class="modal-footer">
                <button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
                <button type="button" class="btn btn-primary submitBtn" onclick="submitContactForm()">SUBMIT</button>
            </div>
        </div>
    </div>
</div>

<script>
function submitContactForm(){
    var reg = /^[A-Z0-9._%+-]+@([A-Z0-9-]+\.)+[A-Z]{2,4}$/i;
    var name = $('#inputName').val();
    var email = $('#inputEmail').val();
    var message = $('#inputMessage').val();
    if(name.trim() == '' ){
        alert('Please enter your name.');
        $('#inputName').focus();
        return false;
    }else if(email.trim() == '' ){
        alert('Please enter your email.');
        $('#inputEmail').focus();
        return false;
    }else if(email.trim() != '' && !reg.test(email)){
        alert('Please enter valid email.');
        $('#inputEmail').focus();
        return false;
    }else if(message.trim() == '' ){
        alert('Please enter your message.');
        $('#inputMessage').focus();
        return false;
    }else{
        $.ajax({
            type:'POST',
            url:'submit_form.php',
            data:'contactFrmSubmit=1&name='+name+'&email='+email+'&message='+message,
            beforeSend: function () {
                $('.submitBtn').attr("disabled","disabled");
                $('.modal-body').css('opacity', '.5');
            },
            success:function(msg){
                if(msg == 'ok'){
                    $('#inputName').val('');
                    $('#inputEmail').val('');
                    $('#inputMessage').val('');
                    $('.statusMsg').html('<span style="color:green;">Thanks for contacting us, we\'ll get back to you soon.</p>');
                }else{
                    $('.statusMsg').html('<span style="color:red;">Some problem occurred, please try again.</span>');
                }
                $('.submitBtn').removeAttr("disabled");
                $('.modal-body').css('opacity', '');
            }
        });
    }
}
</script>

Send Contact Request Email (submit_form.php)

<?php
if(isset($_POST['contactFrmSubmit']) && !empty($_POST['name']) && !empty($_POST['email']) && (!filter_var($_POST['email'], FILTER_VALIDATE_EMAIL) === false) && !empty($_POST['message'])){
    
    // Submitted form data
    $name   = $_POST['name'];
    $email  = $_POST['email'];
    $message= $_POST['message'];
    
    /*
     * Send email to admin
     */
    $to     = 'admin@example.com';
    $subject= 'Contact Request Submitted';
    
    $htmlContent = '
    <h4>Contact request has submitted at CodexWorld, details are given below.</h4>
    <table cellspacing="0" style="width: 300px; height: 200px;">
        <tr>
            <th>Name:</th><td>'.$name.'</td>
        </tr>
        <tr style="background-color: #e0e0e0;">
            <th>Email:</th><td>'.$email.'</td>
        </tr>
        <tr>
            <th>Message:</th><td>'.$message.'</td>
        </tr>
    </table>';
    
    // Set content-type header for sending HTML email
    $headers = "MIME-Version: 1.0" . "\r\n";
    $headers .= "Content-type:text/html;charset=UTF-8" . "\r\n";
    
    // Additional headers
    $headers .= 'From: CodexWorld<sender@example.com>' . "\r\n";
    
    // Send email
    if(mail($to,$subject,$htmlContent,$headers)){
        $status = 'ok';
    }else{
        $status = 'err';
    }
    
    // Output status
    echo $status;die;
}