Example on how to send a message through Google Cloud Messaging (GCM, see http://developer.android.com/google/gcm/server.html ) using a simple PHP script

gcm_send.php

<?php
// Replace with real BROWSER API key from Google APIs
$apiKey = "<ENTER API KEY HERE>";

// Replace with real client registration IDs 
$registrationIDs = array( 
						"APA91bGOrAyHktj3DU0H0z4tsu-...",
						"APA91bHr0vERPIe-DHbQGZLBjuj..." 
					);

// Message to be sent
$message = "Testing the wonderful world of GCM. Pretty awesome!";
$messageType = "100002";

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

$fields = array(
                'registration_ids'  => $registrationIDs,
                'restricted_package_name' => 'com.example.myandroidapp',
                'collapse_key'		=> 'somekey_'.$messageType,
                'data'              => array( "KEY_GCM_MESSAGE_TYPE" => $messageType,
                							  "payload" => $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 ) );

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

// Close connection
curl_close($ch);

//echo "Requested: ".json_encode( $fields );
//echo "\n\n<br/><br/>";
echo $result;