Why am i getting this Smarty error?

[Xephon]

the error

Fatal error: Call to a member function on a non-object in C:\Apache2\htdocs\yorov3\functions.php on line 21

if i make the posts diplay code into a function like this

index.php

<?
  session_start();
  require_once("libs.inc.php");
  include 'db.php';
  include 'functions.php';



  if(isset($_SESSION['username'])){
  $username = $_SESSION['username'];
  }

display_news();

  if(empty($_SESSION['username']))
  {
         $smarty->assign("logged_in", 0);
  } else {
         $smarty->assign("logged_in", 1);
  }

 $smarty->display("index.html");

  ?>

and functions.php

<?

  function redirect($url) {
                echo "<script language=\"Javascript\">
                     window.location=\"$url\"
                     </script>";
  }

  function display_news()
  {
      $sql = mysql_query("select * from news");
         if(mysql_num_rows($sql) >= 1)
         {
             $news = array();
             while($rows = mysql_fetch_array($sql, MYSQL_ASSOC))
             {
                 array_push($news, $rows);
             }
             $smarty->assign("news", $news);
         } else {
             $smarty->assign("news", 0);
         }
  }

I get that error

but i dont get it when i dont put the display post code as a function in an included file. like this:

<?
  session_start();
  require_once("libs.inc.php");
  include 'db.php';




  if(isset($_SESSION['username'])){
  $username = $_SESSION['username'];
  }

  $sql = mysql_query("select * from news");
     if(mysql_num_rows($sql) >= 1)
         {
             $news = array();
             while($rows = mysql_fetch_array($sql, MYSQL_ASSOC))
             {
                 array_push($news, $rows);
             }
             $smarty->assign("news", $news);
         } else {
             $smarty->assign("news", 0);
      }

  if(empty($_SESSION['username']))
  {
         $smarty->assign("logged_in", 0);
  } else {
         $smarty->assign("logged_in", 1);
  }

 $smarty->display("index.html");

  ?>

what am i doing wrong?

[Xephon]

ok got it fixed on my own, but i dont know if it is the right way to do it or not

i added

global $smarty

to my function

and now it looks like this:

  function display_news()
  {
      global $smarty;
      $sql = mysql_query("select news.title, news.text_body, news.post_date, users.username from users,
                          news where news.user_id = users.user_id");
         if(mysql_num_rows($sql) >= 1)
         {
             $news = array();
             while($rows = mysql_fetch_array($sql, MYSQL_ASSOC))
             {

             array_push($news, $rows);
         }
        $smarty->assign("news", $news);
     } else {
         $smarty->assign("news", 0);
     }

  }

is there anything wrong with doing it like this? any security concerns or other such things? if so please tell me what is wrong and how to do it the right way.