Error tidak bisa menampilkan komentar

Notice: Undefined variable: id in C:\xampp\htdocs\ppw1\admin\berita_detil.php on line 164

Warning: mysql_fetch_array() expects parameter 1 to be resource, boolean given in C:\xampp\htdocs\ppw1\admin\berita_detil.php on line 165 Berikan Komentar

Notice: Undefined variable: id in C:\xampp\htdocs\ppw1\admin\berita_detil.php on line 183

<?php
$alert = "<div><span>Berikan Komentar</span>";

if(isset($_POST['kirim'])) {
	$error = false;
	$nama = trim($_POST['nama']);
	$email = check_email($_POST['email']);
	$pesan = trim($_POST['pesan']);
	$alert .= "<br><br><span style='color:#c00;'>";
	if (strlen($nama) < 2 || strlen($pesan) < 2) {
		$alert .= "Mohon tulis nama dan komentar dengan benar.<br>";
		$error = true;
	}
	if (!$email) {
		$alert .= "Alamat e-mail anda tidak valid.<br>";
		$error = true;
	}
	if (!verify_code($_POST['randomcode'], $_POST['code'])) {
		$alert .= "Kode salah.<br>";
		$error = true;
	}
	if (!$error) {
		$nama = strip_tags($nama);
		$pesan = strip_tags($pesan);
		mysql_query("INSERT INTO comment (id_berita, nama, email, komentar, tanggal) VALUES ({$id}, '{$nama}', '{$email}', '{$pesan}', NOW() )");

		unset($_POST['nama'],$_POST['email'],$_POST['pesan']);

		$alert .= "Terima kasih atas komentar anda..";
	}
}

$alert .= "</span></div><br>";

echo "<hr><a name='komentar'></a> Komentar<br><br>";

$query = mysql_query("SELECT * FROM comment WHERE id_berita={$id} ORDER BY date");
while ($row = mysql_fetch_array($query)) {
	$nama = $row['nama'];
	$komentar = $row['komentar'];
	$datestamp = $row['tanggal'];
	echo "<div style='border:1px solid;'>{$nama}<br />{$datestamp}<br />{$komentar}</div><br />";
}

$nama = isset($_POST['nama']) ? $_POST['nama'] : "";
$email = isset($_POST['email']) ? $_POST['email'] : "";
$pesan = isset($_POST['pesan']) ? $_POST['pesan'] : "";

echo "<a name='postkomentar'></a> {$alert}";

$temp = create_code();
$code1 = $temp[0];
$code2 = $temp[1];

echo "<div>
<form method='POST' action='berita_detil.php?id={$id}#postkomentar'>
Nama:<br><input name='nama' size='30' type='text' value='{$nama}'><br><br>
E-mail:<br><input name='email' size='30' type='text' value='{$email}'><br><br>
Silahkan tulis komentar anda :<br><textarea cols='45' rows='5' name='pesan'>{$pesan}</textarea><br><br>
Masukkan kode berikut<br> {$code2}
<input type='hidden' id='randomcode' name='randomcode' value='{$code1}' />
<input maxlength='6' size='6' type='text' name='code' />
<input value=' Kirim ' name='kirim' type='submit' />
</form>
</div>";
?>