fcm：发送带有自定义声音的通知-php

Question

我尝试使用Firebase发送通知，发送了通知，但没有自定义声音。

我听到了声音，但是当我尝试替换声音时，我仍然听到默认声音

这是我的代码：

<?php
 $payload = array(
          'to'=>'/topics/TOPIC_NAME',
          'priority'=>'high',
          "mutable_content"=>true,
          "notification"=>array(
                      "title"=> 'TEST',
                      "body"=> 'Hello',
                      "sound"=> "alert.mp3" //=> I tried also "alert"
              )
        );
    $headers = array(
            'Authorization:key = AIza......',
            '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( $payload ) );
    $result = curl_exec($ch );
    curl_close( $ch );
    var_dump($result);
?>

我将声音文件放入res / raw中。.请帮助我。谢谢！！！