$p=htmlspecialchars($_GET["p"], ENT_QUOTES);
$num=30;
if (!!$p) $start=$p*$num;
else $start=0;
$count = mysql_fetch_row(mysql_query("SELECT COUNT(*) FROM table"));
echo "Страница № ";
for ($i=0;$i<$count[0]/$num;$i++) {
  echo "<a href=/?p=".$i.">".$i."</a> / ";
}
$query = mysql_query("SELECT fields...
  FROM table
  LIMIT ".$start.",".$num
);