Salaaam
$sql = "INSERT INTO BOOK(bookname, authorsname, ISBN) VALUES
('".$_POST[bookname]."'' , '".$_POST[authorsname]."',''".$_POST[ISBN]."')";
above line is correct, your code is wrong ,$_POST[ISBN]')";
and add
$host = 'localhost';
$con = mysql_connect($host, $username, $password);
you can also check this page:
http://php.net/manual/en/function.mysql-connect.php
Regards,
Shahrzad
