Annoying oddity with cookies. Help please

Ok so i had my site working well, i had problems with cookies before. But i got them resolved. Then i wanted to add a log out option to drop the cookie.

I have two files reacting differently to the  setcookie("Cookiename","",time()-3600); command.

there is two directorys.

root directory

root/includes/functions.php

functions.php is the file giving me the trouble i think.

Ok so  in root directoy i have a file called stuff.php with a link to drop the id, it then calls setcookie and deletes it. Then redirects to index.php.

ok. So index.php includes functions.php and calls set_id()

set_id() is in functions.php - it tests if the cookie exists, if not it creates one.

Now when i log out, it sees that a cookie doesnt exist and creates one and stories it in the database.  All seems to be working fine.

However, after that if i were to look at a thread.

it would call a function in functions.php

in that function, it does _is_admin($_COOKIE['name']); if it returns true then an additional option pops up.

so i have just reset my cookie and i can see in the database that set_id() in functions.php has added created a new cookie.

However when the _is_admin() and all other functions in functions.php are called, it still detects the old cookie Which i had before i logged out.

Now why would one function in the file act differently from the rest.

Sorry if i explained this bad, but its so hard to explain and its annoying.

The below functions is in functions.php and recognises there is no cookie and creates a new one.

function set_id(){
        
       
        if(isset($_COOKIE['supercookie'])){
        
                  $v =$_COOKIE['supercookie'];
                  //update cookie
                  setcookie("supercookie",$v,time() + 60 * 60 * 24 * 365);
                  
        
        }
        else{
        $charlist =  "abcdefghijklmnopqrstuvwxyz0123456789";
        $c = "";
        
        for($i = 0; $i < 25; $i++ ){
        
              
              $r = rand() % strlen($charlist);
              $c .= $charlist[$r];
        
        
        }
        
        setcookie("supercookie",$c,time() + 60 * 60 * 24 * 365);
        setcookie("FirstArrived","dfffff",time()+60);
        addaction(9,"Set New id.");
        
        mysql_query("INSERT INTO pword (level,lv,scookie) VALUES ('Norm','0','$c')")or die(mysql_error());
        }
        

}

however any other function in functions.php that calls $_cookie['supercookie'] always seems to be returned the admin cookie which i had before i "logged out"