I wrote thte following piece of code:

```
<?php

$username = $_POST['user'];
$password = $_POST['pass'];

$db = new PDO ('mysql:host=localhost;dbname=ozdatabase;charset=utf8', 'root', '');
$db->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);
$db->setAttribute(PDO::ATTR_ERRMODE, 'ERRMODE_EXCEPTION');

$stmt = $db->prepare("SELECT id, users FROM ozusers WHERE username=? AND password=?");
$stmt->execute(array($username, $password));
$rows = $stmt->fetchAll(PDO::FETCH_ASSOC);

$id = $rows['id'];
$user = $rows['users'];

if ($id) {
    print "Logged";
}

else {
    print "not good";
}

?>

```

This is the HTML Form:

```
<form id='login' action='login.php' method='post' accept-charset='UTF-8'>
<fieldset >
<LEGEND>COMMUNICATION</LEGEND>
<input type='hidden' name='submitted' id='submitted' value='1' />

<label for='username' >UserName*:</label>
<input type='text' name='user' id='username' maxlength="50" />

<label for='password' >Password*:</label>
<input type='password' name='pass' id='password' maxlength="50">

<input type='submit' name='Submit' value='Submit' />

</fieldset>
</form>

```

I get an error when trying to login in the page and it's written:
"Fatal error: Call to a member function execute() on a non-object in.. On line 15"

Why is this happening? I followed best practice guide and it showed to use the "execute()" function exactly like that..

Thanks