$table = mysql_query("SELECT * FROM(SELECT * FROM <- Это что такое вообще??????`forum` where `cat` = '".$id."' ORDER BY `time` DESC LIMIT $start,$str) a ORDER BY `top`");
$table = mysql_query("SELECT * FROM `forum` where `cat` = '".$id."' ORDER BY `top` DESC, `time` DESC LIMIT $start,$str");
<?php
$a = 1;
$b =& $a;
unset($a);
echo $b;