哪位好心人帮俺看看啊..php帮俺规范一下

这是前面的出错的源代码.
<?
$qb=$_GET[q];
$q=urlencode($qd);
$qg=rawurlencode($qb);
$num=$_GET[num];
//if ($num="") $num=10;
$start=$_GET[start];
if ($start=="") $start=0;
?>

这是错误提示..


Notice: Use of undefined constant q - assumed 'q' in D:\wwwroot\art1983\wwwroot\search.php on line 2

Notice: Undefined variable: qd in D:\wwwroot\art1983\wwwroot\search.php on line 3

Notice: Use of undefined constant num - assumed 'num' in D:\wwwroot\art1983\wwwroot\search.php on line 5

Notice: Undefined index: num in D:\wwwroot\art1983\wwwroot\search.php on line 5

Notice: Use of undefined constant start - assumed 'start' in D:\wwwroot\art1983\wwwroot\search.php on line 7

Notice: Undefined index: start in D:\wwwroot\art1983\wwwroot\search.php on line 7

o 哦..

谢谢各位了...