Ho questo script:
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<?php
$mysqli = new mysqli("localhost", "Filippo", "filippo", "test");


if (mysqli_connect_errno()) {
printf("Connect failed: %s\n", mysqli_connect_error());
exit();
}
$stmt = $mysqli->prepare("INSERT INTO access VALUES(?,?)");
$stmt->bind_param('ss',$val1,$val2);
$val1 = "ciccio";
$val2 = "pasticcio";
$stmt->execute();
$stmt->close();
$mysqli->close();
?>

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mi da questo errore:

Fatal error: Call to a member function bind_param() on a non-object in /usr/local/apache2/htdocs/insert.php on line 10

eppure a prima vista sembra grammaticalmente corretto....