Hello guys Don't really understand what is the meaning of this pls.
Warning: Cannot modify header information - headers already sent by (output started at /home/uchealon/public_html/db.php:6) in /home/uchealon/public_html/loginusers.php on line 8

here is my code.

PHP Code:

<?php
include ("db.php");
$username = $_POST['username'];
$password = $_POST['password'];

$query = mysql_query("SELECT * FROM users WHERE username = '$username' AND password = '$password' ");
while($row = mysql_fetch_array($query)){
header("location: members.php");
} 
{
echo "Username or Password incorrect Please try again";
include "error.php";
}
?>

your trying to send this to the browser after one of your includes has headers in it.

PHP Code:

header("location: members.php"); 


in your db.php if it has anything to deal with headers you will get this error. thats the only reason i can think of that would cause this error.

When a script includes a header redirect, any output to the browser before the header call will stuff it up. In your case, if db.php throws an error notice or die() message, it's outputting to the header thus wrecking the header('Location:').

I also think this script snipped has logic errors. Why on earth would you want a redirect contained in a while loop? As soon as the loop iterates the first time the page will redirect...

If you use header(); or setcookie(); you must use the functions ob_start() AND ob_end_flush();
Like this:

PHP Code:

<?php
ob_start();
require_once("db.php");

If($_SERVER['REQUEST_METHOD'] == "POST")
{
    $query = mysql_query("SELECT count(1) FROM `users` WHERE username='".$_POST['username']."' AND password='".$_POST['password']."'")or die(mysql_error()); 

    If(mysql_result($query, 0))
    {
        header("location: members.php"); 
    } 
    Else
    { 
        echo 'Username or Password incorrect Please try again'; 
    } 
}
Else
{
    // Your form here..
}

ob_end_flush();
?>

Thanks guys.. but again i try registring and it went on telling me Registration accepted, yet when i try login in the name and password.. keeps on telling me Username or password incorrect. cos i tried it out by using unexit name and password in the DB. to register it goes on and tells me registration accepted but trying login in with the name. and password it woun't go in..

Even the exiting name and password in the DB, same thing it woun't login either, that was what brought out that error i pasted earlier on.. so what's on boad now is. if any person register, it will go in and not submitting infos. and if at all it does it woun't login you in..

So what might be the problem.

Thanks for your help.