header information error

Už jsem zkusil návody na internetu jak chybu odstranit a nic.

Warning: Cannot modify header information - headers already sent by (output started at /CCookieBlock.inc.php on line 23

Na řádku 23 je
function validate(){

<?php
class CCookieBlock
{
function setup( $cookie_key, $period = null ) {
//-- cookie name must not contain '.'
$cookie_key = str_replace( '.', '-', $cookie_key );
$this->cookie_key = $cookie_key;
if ( is_null($period) ) {
$period = 60*60*24*365;}
$this->period = $period;}
function add( $val = 'yes' ) {
setcookie( $this->cookie_key, $val, time() + $this->period );
$_COOKIE[$this->cookie_key] = $val;
return false;}
function get() {
if ( isset($_COOKIE[$this->cookie_key]) ) {
return $_COOKIE[$this->cookie_key];} 
else {return '';}
}
function exists() {
return ( isset($_COOKIE[$this->cookie_key]) );
}
function validate(){
if ( $this->exists() ) {
return false;} 
else 
{return true;}
}
function clear() {
setcookie( $this->cookie_key, "", time()-3600 );
return true;
}
}
?>

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