Ошибка DB ERROR: You have an error in your SQL syntax; check the manual that corresponds to your MySQL serv

<?php
/*Подключаемся к БД*/
$db = mysql_connect('localhost','Zelix','123');
mysql_select_db('basa_site', $db);
/*Делаем запрос к БД*/
 
$num = $_GET['num'];
 
$result = mysql_query("SELECT * FROM new_posts ORDER BY id DESC LIMIT ($num), 6",$db);
if (!$result) {
echo 'DB ERROR: ' . mysql_error();
exit;
}
/*Преобразовываем результат в массив*/
$new_post = array();
while($row = mysql_fetch_array($result))
{
$new_post[] = $row;
$id = $row['id'];
$avtor = $row['avtor'];
$name = $row['name'];
$rybrika = $row['rybrika'];
$text = $row['text'];
$data_reg = $row['data_reg'];
$foto = $row['foto'];
}
 
echo json_encode ($new_post);
?>

$result = mysql_query("SELECT * FROM new_posts ORDER BY id DESC LIMIT ($num), 6",$db);

$num = isset($_GET['num']) ? (int) $_GET['num'] : 0;

$result = mysql_query("SELECT * FROM new_posts ORDER BY id DESC LIMIT $num, 6",$db);

$result = mysql_query("SELECT * FROM new_posts ORDER BY id DESC LIMIT $num, 6",$db);

<?php
/*Подключаемся к БД*/
$db = mysql_connect('localhost','Zelix','123');
mysql_select_db('basa_site', $db);
/*Делаем запрос к БД*/
 
$num = isset($_GET['num']) ? (int) $_GET['num'] : 0;
$perPage = 6;
$start = $num * $perPage;
 
$result = mysql_query("SELECT * FROM new_posts ORDER BY id DESC LIMIT $start, $perPage",$db);