notification.php

<?php

// buka koneksi databse
include 'koneksi.php';

if($_POST){
    include 'firebase.simple.php';
    $firebase = new Firebase('AAAABlcS_6E:APA91bEnfKljgWx90Ar9JknT07GkkY2b16mXj2UBf3HRtiqBG7EFxmuprufq_Snv9Eby9w8mkuthUvu9hju5F_9G6dtdiFRsAyIuMvHFj5g4yvV_tvCkejwRDrP1QN4zjJmuvyfBPGxy
');

    $firebase->setMessage('Judul', 'Isi Pesan (optional)');
    $firebase->setTarget($_POST['penerima']);
    $kirim = $firebase->send();
    $hasil = $firebase->send();
    $hasil = json_decode($hasil,true);

    echo '<pre>';
    print_r($hasil);
    echo '</pre>';
}

echo '<form action="" method="post">
<p><label>Judul : <input type="text" name="judul" placeholder="Judul Notif" /></p>
<p><label>Pesan : <input type="text" name="pesan" placeholder="Pesan Notif" /></p>
<p><label>Penerima : ';
$user = $mysqli->query("SELECT nama,token from tbl_user WHERE token!=''");
while($row = $user->fetch_assoc()){
    echo "<label><input type=\"checkbox\" name=\"penerima[]\" value=\"$row[token]\" /> $row[nama]</label><br />";
}
echo '</p>
<p><input type="submit" value="Kirim" /></p>
</form>';