这段代码终于为我工作了。

 <？php 
函数send_notification（$ tokens）
 {

 $ url ='https://fcm.googleapis.com/fcm/send'; 
 $ priority =high; 
 $ notification = array（'title'=>'Some title'，'body'=>'hi'）; 

 $ fields = array（
'registration_ids'=> $ tokens，
'notification'=> $ notification 

）; 

 $ b $ header = array（
'Authorization：key = xxxxxxxxxxxxx'，
'Content-Type：application / json'
）; 

 $ ch = curl_init（）; 
 curl_setopt（$ ch，CURLOPT_URL，$ url）; 
 curl_setopt（$ ch，CURLOPT_POST，true）; 
 curl_setopt（$ ch，CURLOPT_HTTPHEADER，$ headers）; 
 curl_setopt（$ ch，CURLOPT_RETURNTRANSFER，true）; 
 curl_setopt（$ ch，CURLOPT_SSL_VERIFYHOST，0）; 
 curl_setopt（$ ch，CURLOPT_SSL_VERIFYPEER，false）; 
 curl_setopt（$ ch，CURLOPT_POSTFIELDS，json_encode（$ fields））; 
 // echo json_encode（$ fields）; 
 $ result = curl_exec（$ ch）; 
 echo curl_error（$ ch）; 
 if（$ result === FALSE）{
 die（'Curl failed：'。curl_error（$ ch））; 
} 
 curl_close（$ ch）; 
返回$ result; 
} 
 $ tokens = array（'RECEIVER-TOKEN-1'
，'RECEIVER_TOKEN-2'）; 

 $ message_status = send_notification（$ tokens）; 
 echo $ message_status; 
？> 
 

PS：我现在硬编码接收器令牌（用于测试目的）

I'm trying to write an application to receive notifications via Firebase Cloud Messaging. It initially worked when I tried to send the message via Firebase console but then the moment I tried doing the same using php webservice, in response, it showed success but I neither received the message nor am I able to get any more notifications via firebase console. Please help

My server side code:

MainActivity.java

package com.example.mojojojo.firebasenotifications;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.SharedPreferences;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.widget.EditText;

import com.google.firebase.iid.FirebaseInstanceId;

public class MainActivity extends AppCompatActivity {

    private EditText etToken;
    private SharedPreferences sp;
    private SharedPreferences.Editor edit;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        etToken=(EditText)findViewById(R.id.etToken);

        sp=getSharedPreferences("pref",MODE_PRIVATE);
        edit=sp.edit();

        etToken.setText(FirebaseInstanceId.getInstance().getToken());
        BroadcastReceiver tokenReceiver=new BroadcastReceiver() {
            @Override
            public void onReceive(Context context, Intent intent) {
                String token=intent.getExtras().getString("token");
                if(token!=null){
                    etToken.setText(token);
                }
            }
        };
        registerReceiver(tokenReceiver,new IntentFilter("TOKEN_GENERATED"));
    }
}

Messaging service

package com.example.mojojojo.firebasenotifications;

import android.app.NotificationManager;
import android.app.PendingIntent;
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.media.RingtoneManager;
import android.net.Uri;
import android.os.IBinder;
import android.support.v4.app.NotificationCompat;
import android.util.Log;

import com.google.firebase.messaging.FirebaseMessagingService;
import com.google.firebase.messaging.RemoteMessage;

public class MessagingService extends FirebaseMessagingService {

    @Override
    public void onMessageReceived(RemoteMessage remoteMessage) {
        super.onMessageReceived(remoteMessage);
        String msg=remoteMessage.getNotification().getBody();
        sendNotification(msg);
        Log.i("/>/>",msg);
    }
    private void sendNotification(String messageBody) {
        Intent intent = new Intent(this, MainActivity.class);
        intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
        PendingIntent pendingIntent = PendingIntent.getActivity(this, 0 , intent,
                PendingIntent.FLAG_ONE_SHOT);

        Uri defaultSoundUri= RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
        NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this)
                .setSmallIcon(R.mipmap.ic_launcher)
                .setContentTitle("FCM Message")
                .setContentText(messageBody)
                .setAutoCancel(true)
                .setSound(defaultSoundUri)
                .setContentIntent(pendingIntent);

        NotificationManager notificationManager =
                (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);

        notificationManager.notify(0 , notificationBuilder.build());
    }
}

Token Service

package com.example.mojojojo.firebasenotifications;

import android.app.Service;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.IBinder;

import com.google.firebase.iid.FirebaseInstanceId;
import com.google.firebase.iid.FirebaseInstanceIdService;

public class TokenService extends FirebaseInstanceIdService {
    private SharedPreferences sp;
    private SharedPreferences.Editor edit;

    @Override
    public void onTokenRefresh() {
        super.onTokenRefresh();

        sp=getSharedPreferences("pref",MODE_PRIVATE);
        edit=sp.edit();

        String token= FirebaseInstanceId.getInstance().getToken();
        edit.putString("token",token);

        Intent tokenIntent=new Intent("TOKEN_GENERATED");
        tokenIntent.putExtra("token",token);
        sendBroadcast(tokenIntent);
    }
}

Manifest

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.mojojojo.firebasenotifications">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <service
            android:name=".MessagingService"
            android:enabled="false"
            android:exported="false" >
            <intent-filter>
                <action android:name="com.google.firebase.MESSAGING_EVENT"/>
            </intent-filter>
        </service>

        <service
            android:name=".TokenService">
            <intent-filter>
                <action android:name="com.google.firebase.INSTANCE_ID_EVENT"/>
            </intent-filter>
        </service>
    </application>

</manifest>

and my php code is as follows (I've removed the server Key in the code)

<?php
define( 'API_ACCESS_KEY', 'YOUR-API-ACCESS-KEY-GOES-HERE' );
$registrationIds = array( $_GET['id'] );
// prep the bundle
$msg = array
(
    'message'   => 'hi',
    'title'     => 'This is a title. title',
    'subtitle'  => 'This is a subtitle. subtitle',
    'tickerText'    => 'Ticker text here...Ticker text here...Ticker text here',
    'vibrate'   => 1,
    'sound'     => 1,
    'largeIcon' => 'large_icon',
    'smallIcon' => 'small_icon'
);
$fields = array
(
    'registration_ids'  => $registrationIds,
    'data'          => $msg
);

$headers = array
(
    'Authorization: key=' . 'xxxxxxxxxxxxxxxxxxxxx',
    'Content-Type: application/json'
);

$ch = curl_init();
curl_setopt( $ch,CURLOPT_URL, 'https://fcm.googleapis.com/fcm/send' );
curl_setopt( $ch,CURLOPT_POST, true );
curl_setopt( $ch,CURLOPT_HTTPHEADER, $headers );
curl_setopt( $ch,CURLOPT_RETURNTRANSFER, true );
curl_setopt( $ch,CURLOPT_SSL_VERIFYPEER, false );
curl_setopt( $ch,CURLOPT_POSTFIELDS, json_encode( $fields ) );
$result = curl_exec($ch );
curl_close( $ch );
echo $result;
?>

This php code finally worked for me.

<?php 
function send_notification ($tokens)
{

    $url = 'https://fcm.googleapis.com/fcm/send';
    $priority="high";
    $notification= array('title' => 'Some title','body' => 'hi' );

    $fields = array(
         'registration_ids' => $tokens,
         'notification' => $notification

        );


    $headers = array(
        'Authorization:key=xxxxxxxxxxxxx',
        'Content-Type: application/json'
        );

   $ch = curl_init();
   curl_setopt($ch, CURLOPT_URL, $url);
   curl_setopt($ch, CURLOPT_POST, true);
   curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
   curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
   curl_setopt ($ch, CURLOPT_SSL_VERIFYHOST, 0);  
   curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
   curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($fields));
    // echo json_encode($fields);
   $result = curl_exec($ch);           
   echo curl_error($ch);
   if ($result === FALSE) {
       die('Curl failed: ' . curl_error($ch));
   }
   curl_close($ch);
   return $result;
}
$tokens = array('RECEIVER-TOKEN-1'
    ,'RECEIVER_TOKEN-2');

  $message_status = send_notification($tokens);
  echo $message_status;
?>

P.S: I've hard coded the receiver tokens as of now (for testing purposes)