ผมอยากทำ Alert ของ Javascript ให้ใช้งานได้บน php ครับ

<?php
	session_start();
	mysql_connect("localhost","root","jjazz0023");
	mysql_select_db("fox");
	$strSQL = "select * from student where code = '".mysql_real_escape_string($_POST['txtUsername'])."'
	and pin_id = '".mysql_real_escape_string($_POST['txtPassword'])."'";
	$objQuery = mysql_query($strSQL);
	$objResult = mysql_fetch_array($objQuery); if(!$objResult) { echo "Username And Password Incorrect!"; } else 
	{ $_SESSION["UserID"] = $objResult["UserID"]; $_SESSION["Status"] = $objResult["Status"]; session_write_close();
	if($objResult["Status"] == "ADMIN") { header("location:../admin/admin_page.php"); } else { header("location:../user/user_page.php"); } } mysql_close();
	?>