if (preg_match('/^[1-9][0-9]*&/', $_GET['id'])) {
    $id =(int)$_GET['id'];
} else {
    echo "不正なIDです！";
    exit;
}

&stmt = $dbh->prepare("select * from intries where id = :id limit 1");
$stmt->execute(array(":id" => $id));
$entry = $stmt->fetch() or die("no one found!");
$name = $entry['name'];
$email = $entry['email'];
$memo = $entry['memo'];