function assignment_send_push($pushMessage, $post_id, $deadline, $reg_ids)
{
    $fire = new FirebasePush($pushMessage);
    $fire->sendPushNotification();
    $message = array("assignment" => $pushMessage, "assignmentID" => $post_id, "assignmentDeadline" => $deadline);
    send_push_notification($reg_ids, $message);
    update_post_meta($post_id, 'notified', "1");
}
<?php

/**
 * Created by PhpStorm.
 * User: Ahereza
 * Date: 12/10/16
 * Time: 00:40
 */
require_once 'FirebasePush.php';
$response = array();
if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    //hecking the required params
    if (isset($_POST['message'])) {
        $fire = new FirebasePush($_POST['message']);
        $fire->sendPushNotification();
    }
}