<?php

if (!isset($_POST['accedi'])){
echo'<form action="" method="POST">
Username<input type="text" name="username" />


Password<input type="text" name="password" />


<input type="submit" name="accedi" value="accedi" />
</form>';

} else{

include ("config.php");

}

$username=mysql_real_escape_string($_POST['username']);
$password=mysql_real_escape_string($_POST['password']);

$query="INSERT INTO accesso (username, password) VALUES('{$username}', '{$password}')";
$result = mysql_query($query,$conn) or die (mysql_error());
?>


ho modificato cosi ma mi spunta sempre un warning:
Warning: mysql_query() expects parameter 2 to be resource, null given in C:\Program Files (x86)\EasyPHP-5.3.8.1\www\login.php on line 20

come risolvoo