许多教程都过时了，甚至当前的代码都没有考虑设备注册id何时更新或设备取消注册。如果不检查这些项目，最终将导致无法接收消息的问题。http://forum.loungekatt.com/viewtopic.php?t=63#p181

<?php
    // Replace with the real server API key from Google APIs
    $apiKey = "your api key";

    // Replace with the real client registration IDs
    $registrationIDs = array( "reg id1","reg id2");

    // Message to be sent
    $message = "hi Shailesh";

    // Set POST variables
    $url = 'https://android.googleapis.com/gcm/send';

    $fields = array(
        'registration_ids' => $registrationIDs,
        'data' => array( "message" => $message ),
    );
    $headers = array(
        'Authorization: key=' . $apiKey,
        'Content-Type: application/json'
    );

    // Open connection
    $ch = curl_init();

    // Set the URL, number of POST vars, POST data
    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_POSTFIELDS, json_encode( $fields));

    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
    // curl_setopt($ch, CURLOPT_POST, true);
    // curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode( $fields));

    // Execute post
    $result = curl_exec($ch);

    // Close connection
    curl_close($ch);
    echo $result;
    //print_r($result);
    //var_dump($result);
?>

这段代码将通过PHP CURL向多个注册id发送一个GCM消息。

// Payload data you want to send to Android device(s)
// (it will be accessible via intent extras)    
$data = array('message' => 'Hello World!');

// The recipient registration tokens for this notification
// https://developer.android.com/google/gcm/    
$ids = array('abc', 'def');

// Send push notification via Google Cloud Messaging
sendPushNotification($data, $ids);

function sendPushNotification($data, $ids) {
    // Insert real GCM API key from the Google APIs Console
    // https://code.google.com/apis/console/        
    $apiKey = 'abc';

    // Set POST request body
    $post = array(
                    'registration_ids'  => $ids,
                    'data'              => $data,
                 );

    // Set CURL request headers 
    $headers = array( 
                        'Authorization: key=' . $apiKey,
                        'Content-Type: application/json'
                    );

    // Initialize curl handle       
    $ch = curl_init();

    // Set URL to GCM push endpoint     
    curl_setopt($ch, CURLOPT_URL, 'https://gcm-http.googleapis.com/gcm/send');

    // Set request method to POST       
    curl_setopt($ch, CURLOPT_POST, true);

    // Set custom request headers       
    curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);

    // Get the response back as string instead of printing it       
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

    // Set JSON post data
    curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($post));

    // Actually send the request    
    $result = curl_exec($ch);

    // Handle errors
    if (curl_errno($ch)) {
        echo 'GCM error: ' . curl_error($ch);
    }

    // Close curl handle
    curl_close($ch);

    // Debug GCM response       
    echo $result;
}

使用这个

 function pnstest(){

                $data = array('post_id'=>'12345','title'=>'A Blog post', 'message' =>'test msg');

                $url = 'https://fcm.googleapis.com/fcm/send';

                $server_key = 'AIzaSyDVpDdS7EyNgMUpoZV6sI2p-cG';

                $target ='fO3JGJw4CXI:APA91bFKvHv8wzZ05w2JQSor6D8lFvEGE_jHZGDAKzFmKWc73LABnumtRosWuJx--I4SoyF1XQ4w01P77MKft33grAPhA8g-wuBPZTgmgttaC9U4S3uCHjdDn5c3YHAnBF3H';

                $fields = array();
                $fields['data'] = $data;
                if(is_array($target)){
                    $fields['registration_ids'] = $target;
                }else{
                    $fields['to'] = $target;
                }

                //header with content_type api key
                $headers = array(
                    'Content-Type:application/json',
                  'Authorization:key='.$server_key
                );

                $ch = curl_init();
                curl_setopt($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));
                $result = curl_exec($ch);
                if ($result === FALSE) {
                    die('FCM Send Error: ' . curl_error($ch));
                }
                curl_close($ch);
                return $result;

}

你也可以试试下面这段代码:

<?php
    define("GOOGLE_API_KEY", "AIzaSyCJiVkatisdQ44rEM353PFGbia29mBVscA");
    define("GOOGLE_GCM_URL", "https://android.googleapis.com/gcm/send");

    function send_gcm_notify($reg_id, $message) {
        $fields = array(
            'registration_ids'  => array( $reg_id ),
            'data'              => array( "message" => $message ),
        );

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

        $ch = curl_init();
        curl_setopt($ch, CURLOPT_URL, GOOGLE_GCM_URL);
        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);
        if ($result === FALSE) {
            die('Problem occurred: ' . curl_error($ch));
        }

        curl_close($ch);
        echo $result;
    }

    $reg_id = "APA91bHuSGES.....nn5pWrrSz0dV63pg";
    $msg = "Google Cloud Messaging working well";

    send_gcm_notify($reg_id, $msg);

你可以在packagist上使用这个PHP库:

https://github.com/CoreProc/gcm-php

安装后，你可以这样做:

$gcmClient = new GcmClient('your-gcm-api-key-here');

$message = new Message($gcmClient);

$message->addRegistrationId('xxxxxxxxxx');
$message->setData([
    'title' => 'Sample Push Notification',
    'message' => 'This is a test push notification using Google Cloud Messaging'
]);

try {

    $response = $message->send();

    // The send() method returns a Response object
    print_r($response);

} catch (Exception $exception) {

    echo 'uh-oh: ' . $exception->getMessage();

}