session problem!!pls help me

i tried the shoping cart tutorial in http://www.devarticles.com/art/1/132/3
i sucess to build the cart but when i use same method in my final project which related e-commerce have problem in db.php in line
setcookie("cartId", session_id(), time() + ((3600 * 24) * 30));

*php code

function GetCartId()
{
if(isset($_COOKIE["cartId"]))
{
return $_COOKIE["cartId"];
}
else
{

session_start();
setcookie("cartId", session_id(), time() + ((3600 * 24) * 30)); (line 43)
return session_id();
}
}

it have error:
Warning: Cannot send session cache limiter - headers already sent (output started at c:\web\wai\cart.php:3) in c:\web\db.php on line 43

i have put all document with <?session_start();?> in beginning of coding but still got same problem

pls help me.it is urgent for my final year project.10q

It sounds like you're sending content before the cookie headers - check line 43 in db.php and make sure you aren't sending anything to the browser (eg. print, echo, or a trailing new line).

Hadley

did you use the ob_start(); function to clear the headers?

and don't forget ob_end_flush(); as i did or else you'll spend many hours sifting back over your code and driving your self crazy

i've found that using ob_end_clean(); in similar cases works magic ! also, you may need to call the function through the ob_start() function...

like:

ob_start("$functionname");

.....
.....
.....

ob_end_clean();

(you needn't specify the function name when flushing )

It's probably best to do a little more research and find out what the problem actually is - if it's just a trailing newline (which is very easy to add accidentally) it will be easily fixed. Blindly using output buffering is overkill.

Hadley

i never use ob_start before tat.

Is it i have to add the new ob_start function in db.php?

Is it ob_start have to put before all coding start?

or i just add in my funtion GetcartID?

ob_start(GetcardID)?

php code*

ob_start("$functionname");

.....
.....
.....

ob_end_clean();

WHAT can write inside the ............

thank you very much 4 your kindly to reply my Q.