Login page

Login page php code

   <?php

if($_SESSION['UserID']!='')
{
echo '<META HTTP-EQUIV="Refresh" Content="0; URL=main.php">';
}
?>
<?php

$UserName = $_POST["txtUser"];
$userCheck = 0;
if ($UserName != null)
{
$Password =  $_POST["txtPassWord"];


$db =  new LoginDBManager();
$SQL = "SELECT
`user`.id,
`user`.username,
`user`.email,
`user`.`password`
FROM
user` WHERE username='$UserName' AND password='".md5($Password)."';";
$SQL ="SELECT UserID FROM users where UserName='". $UserName."' and                                    Password='". md5($Password) ."';";

echo $SQL;
$result = $db->RunQuery($SQL);
$validUser = false;

$db = NULL;
if(mysql_num_rows($result)>0)
{
while($row = mysql_fetch_array($result))
{

$_SESSION["UserID"] = $row["id"];
$_SESSION["UserName"] = $row["username"];
$_SESSION["Password"] = $row["password"];
}
echo '<META HTTP-EQUIV="Refresh" Content="0;                                                                              URL=main.php">';
}
else
//$userCheck= "User Name / Password Error";
echo "<script>alert('User Name / Password Error')</script>";

}?>