显示图像配置文件:PHP

我的问题是，当我提交按钮时，页面中的内容会消失，然后当我刷新页面时，图片会正常显示所有内容。所以我不明白为什么在提交后我必须刷新页面以显示图片。

<div class="widget">
    <h2>Hello, <?php echo $user_data['first_name'].' ' . $user_data['last_name']; ?>!</h2>
    <div class="inner">
        <div class="profile">
            <?php
            if(isset($_FILES['profile']) == true)
            {
                if(empty($_FILES['profile']['name']) == true)
                {
                    echo 'Please choose a file!';
                }
                else
                {
                    $allowed = array('jpg', 'jpeg', 'gif', 'png');
                    $file_name = $_FILES['profile']['name'];
                    $file_size = $_FILES['profile']['size'];
                    $file_extn = strtolower(end(explode('.', $file_name)));
                    $file_temp = $_FILES['profile']['tmp_name'];

                    if(in_array($file_extn, $allowed) == true && $file_size<(1024*1024) == true)
                    {
                        change_profile_image($session_user_id, $file_temp, $file_extn);

                        exit();
                    }
                    else if($file_size<(1024*1024) == false)
                    {
                        echo  "Image file size max 1 MB"; 
                    }
                    else
                    {
                        echo 'Incorrect file type. Allowed: ';
                        echo implode(', ', $allowed);
                    }
                }
            }
            if(file_exists($user_data['profile']))
            {
                echo '<img src="', $user_data['profile'], '" alt="', $user_data['first_name'], ' ''s Profile Image">';
            }
            else
            {
                echo '<img src="./images/profile/default.gif" height="180"><br>';
                echo '<strong>Upload your picture</strong>';
            }
            ?>
             <form action="" method="post" enctype="multipart/form-data">
                <input type="file" name="profile"> <input type="submit">
            </form>
        </div>
        <ul>
            <li>
                <a href="logout.php">Log out</a>
            </li>
            <li>
                <a href="<?php echo $user_data['username']; ?>">Profile</a>
            </li>
            <li>
                <a href="changepassword.php">Change password</a>
            </li>
            <li>
                <a href="settings.php">Settings</a>
            </li>
        </ul>
    </div>
</div>

这就是功能：

function change_profile_image($user_id, $file_temp, $file_extn)
{
    $file_path = 'images/profile/' . substr(md5(time()), 0, 10) . '.' . $file_extn ;
    move_uploaded_file($file_temp, $file_path);
    mysql_query("UPDATE users SET profile = '" . $file_path .  "' WHERE user_id = "  . (int)$user_id);
}