YA: Login Script Fixes 20120718042308AAQcU81 WC

<?php
// Needs to be started before anything has been sent to the user, including whitespace.
session_start();

if(isset($_POST['Submit'])){
    include 'connection/conn.php';
    $database="issuelog";
    $selectdb = mysql_selectdb($database);
    if ($selectdb){
        echo "Selected";
        $UserName = $_POST['username'];
        // Password's should never be stored as plain text.
        $Password = $_POST['password'];
        $table = "userreg";
        $sql = "SELECT UserName FROM $table WHERE UserName='{$UserName}' AND Password='{$Password}' LIMIT 1";

        // Including the Connection Resource Link in the query call is the best way. Good Job.
        $results=mysql_query($sql, $conn);

        // Check for successful query
        if( $results && mysql_num_rows($results) === 1){
            // If successful login details, redirect user to 'login_success.php'
            // session_register() is no longer a valid function. It is deprecated in PHP 5.3 and removed from 5.4
            $_SESSION['username'] = $UserName;
            $_SESSION['password'] = $Password;
            if( !headers_sent()){ // Check to see if the headers have already been sent. You cannot send more if they have already been sent.
                header("Location: login_success.php");
                exit;
            }else{
                // If the headers have been sent, send alternative redirect methods.
                echo '<meta http-equiv="refresh" content="0; url=login_success.php"/>');
                echo '<script>document.location.href="login_success.php";</script>';
                exit;
            }
        } else if( !$results ){
            // Query Failed, either because of a server/mysql error
            // or a malformed query statement.
            // echo 'Query [' . $sql . '] Failed because: ' . mysql_error($conn); // Uncomment this line for debugging purposes only
            echo 'Internal Server Error';
        } else {
            echo "Wrong Username or Password.";
        }
    }
}
?>

login_success.php
<?php
session_start();
if(!isset($_SESSION['username'])){
    header("Location: login.php");
}
?>

<html>
    <body>
        Login Successful
    </body>
</html>