FCM通知如何使用php发送图像？

Question

我想使用以下代码发送带有图像的通知，但仍然无法正常工作

{
    $msg = array
    (
        'body'  => 'here is a message. message',
        'title'     => 'This is a title',
        'subtitle'  => 'This is a subtitle. subtitle',
        'vibrate'   => 1,
        'sound'     => 1,
        'icon'  => 'url_image',
        'image' => 'url_image'
    );
    $fields = array
    (
        'registration_ids'  => array('id1','id2'),
        'notification'          => $msg,

    );

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

    $ch = curl_init();
    curl_setopt( $ch,CURLOPT_URL, 'url of fcm ' );
    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 );
}

我收到没有图像的通知

有什么解决方案？