Why am i getting this error?

Dangmnx

// Check if session is not registered , redirect back to main page. // Put this code in first line of web page.
Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at /home/dangmnne/public_html/hp/login_success.php:3) in /home/dangmnne/public_html/hp/login_success.php on line 4
Login Successful

the link is
http://www.dangmn.net/hp/login_success.php

the script is

// Check if session is not registered , redirect back to main page.
// Put this code in first line of web page.
<?
session_start();
if(!session_is_registered(myusername)){
header("location:main_login.php");
}
?>

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

coldwerturkey

you have output before you declare your headers. you can't do that.

put the php comments within the php tags

bradgrafelman

Speaking of other things wrong with that code:

Use the full '<?php' tags; short tags has been deprecated for some time now. It's disabled by default in resent PHP versions and even removed altogether from PHP6.
Likewise, [man]session_is_registered/man and its cousin, [man]session_register/man have both been deprecated. Instead, use the $_SESSION superglobal array (e.g. use [man]isset/man to check if a variable exists). More information about this array can be found here: [man]variables.server[/man].
Technically, you're supposed to use a full URI in a Location header (e.g. 'Location: http://mysite.com/index.php'). Still, one suggestion I might make is to add an [man]exit[/man] after a header('Location: ...') call so that PHP stops executing the rest of the code (since there's no need to do so, in this case).