<?php
// $viewusername ="";
// $viewcontactnumber = "";
// $viewaddress = "";
// $viewcountry = "";
// $viewcity = "";
// $viewzipcode = "";

if ($_SERVER['REQUEST_METHOD'] == "POST") {
    if (ISSET($_POST['mydata'])) {
    $host = 'localhost';
    $user = 'root';
    $pass ='';
    $db = 'valocy';

    $con = mysqli_connect($host,$user,$pass,$db) or die(mysqli_error());
    $sql = "SELECT * FROM addressdetails WHERE email='haroondar0037@gmail.com'";
        if ($result = mysqli_query($con, $sql)) {
            if (mysqli_num_rows($result > 0)) {
                WHILE ($resultarr = mysqli_fetch_assoc($result)) {
                    $viewusername = $resultarr['fullname'];
                    // $viewusername = htmlspecialchars($resultarr['fullname'],ENT_QUOTES);
                    // $viewcontactnumber = $resultarr['contactnumber'];
                    // $viewaddress = $resultarr['address'];
                    // $viewcountry = $resultarr['country'];
                    // $viewcity = $resultarr['city'];
                    // $viewzipcode = $resultarr['zipcode'];
                }
            } else {
                // use ELSE for better troubleshooting
                echo 'Warning: No record found';
            }
        } else {
            echo 'Error :' . mysqli_error($con);
        }
    }
}
?>
<?php include('includes/header.php'); ?>

<br><br><br><br><br>
<div class="col-sm-offset-3 col-sm-2 col-xs-offset-3" style="margin-top:5px;">
    <form method="POST" action="">
        <button type="submit" name="mydata" class="btn btn-info btn-lg" data-toggle="modal" data-target="#myModal">View My Data</button>
    </form>
</div>

<!-- Modal -->
<div id="myModal" class="modal fade" role="dialog">
    <div class="modal-dialog">
        <!-- Modal content-->
        <div class="modal-content">
            <div class="modal-header">
            <button type="button" class="close" data-dismiss="modal">&times;</button>
            <h4 class="modal-title">Your Data</h4>
            </div>
            <div class="modal-body">
<?php
    // check your $viewusername if is set here
    // coz you $viewusername may not be set due to no POST or query failure or no query result
    if (ISSET($viewusername)) {
        echo "name: $viewusername";
    } else {
        echo "name:";
    }
?>
            </div>
            <div class="modal-footer">
                <input type="button" name="close" value="close" class="btn btn-default" data-dismiss="modal">
            </div>
        </div>
    </div>
</div>