<?php

$duzey = intval($_POST['duzey']);
$soru = intval($_POST['soru']);

foreach($_POST["dersler"] as $k) $dersler[]= '"'.$k.'"';

$dersler = implode(",", $dersler); 
$sorgu = mysql_query('select * from soru_test where ders in ('.$dersler.') and duzey= "'.$duzey.'" LIMIT '.$soru);  

?>