ถามวิธีทำให้หน้าต่าง log in แสดงข้อความ เมื่่อผู้ใช้กรอกยูสเซอร์ หรือพาสเวิร์ดผิด

<div id="login-box" class="login-popup">
        <a href="#" class="close"><img src="images/close_pop.png" class="btn_close" title="Close Window" alt="Close" /></a>
		
          <form method="post" class="signin" action="validate.php">
		  
				
                <fieldset class="textbox">
            	<label class="username">
                <input id="username" name="username" type="text" value="" autocomplete="on" placeholder="Username">
                </label>
                
                <label class="password">
                <input id="password" name="password" value=""type="password" placeholder="Password">
                </label>
                
                <button class="loginbutton" type="submit button"><a>Sign in</a></button>
                
                
                <a class="style1" href="#"><span>Forgot your password?</span></a>
                
                </fieldset>
			</form>
		</div>

<?

$dbname="../private/viagroupDB.s3db";
$db = new PDO("sqlite:$dbname");
 
 
session_start();
$usn = $_POST['username'];
$pwd = $_POST['password'];

$sql="SELECT username,password FROM viamember;";
    foreach ($db->query($sql) as $row){
		if(($row['username']==$usn)&&($row['password']==$pwd)){
			?>
			<script language="javascript">
				window.location.href="via_dig.html"
			</script> 
			<?php
		}else{
			
		}
	 }


?>