send_fcm_message_using_http_v1.php

<?php

/**
 * Gets an access token for FCM API calls
 * @param string $serviceAccountPath Path to your service account JSON file
 * @return string The access token
 */
function getAccessToken($serviceAccountPath) {
    $serviceAccount = json_decode(file_get_contents($serviceAccountPath), true);
    
    // Create JWT
    $now = time();
    $jwt = [
        'iss' => $serviceAccount['client_email'],
        'scope' => 'https://www.googleapis.com/auth/firebase.messaging',
        'aud' => 'https://oauth2.googleapis.com/token',
        'exp' => $now + 3600,
        'iat' => $now
    ];
    
    // Encode JWT Header
    $jwtHeader = base64_encode(json_encode(['alg' => 'RS256', 'typ' => 'JWT']));
    $jwtHeader = str_replace(['+', '/', '='], ['-', '_', ''], $jwtHeader);
    
    // Encode JWT Payload
    $jwtPayload = base64_encode(json_encode($jwt));
    $jwtPayload = str_replace(['+', '/', '='], ['-', '_', ''], $jwtPayload);
    
    // Create JWT Signature
    $jwtSignature = $jwtHeader . '.' . $jwtPayload;
    $key = $serviceAccount['private_key'];
    openssl_sign($jwtSignature, $signature, $key, 'SHA256');
    $jwtSignature = base64_encode($signature);
    $jwtSignature = str_replace(['+', '/', '='], ['-', '_', ''], $jwtSignature);
    
    // Create signed JWT
    $signedJwt = $jwtHeader . '.' . $jwtPayload . '.' . $jwtSignature;
    
    // Exchange JWT for access token
    $ch = curl_init('https://oauth2.googleapis.com/token');
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_POST, true);
    curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query([
        'grant_type' => 'urn:ietf:params:oauth:grant-type:jwt-bearer',
        'assertion' => $signedJwt
    ]));
    
    $response = curl_exec($ch);
    curl_close($ch);
    
    $token = json_decode($response, true);
    return $token['access_token'];
}

/**
 * Sends an FCM message to a topic using the HTTP v1 API
 * @param string $serviceAccountPath Path to your service account JSON file
 * @param string $projectId Your Firebase project ID
 * @param string $topic The FCM topic to send to (without the /topics/ prefix)
 * @param array $data Optional data payload
 * @return array The response from FCM
 */
function sendFCMMessageToTopic($serviceAccountPath, $projectId, $topic, $data = []) {
    $url = "https://fcm.googleapis.com/v1/projects/{$projectId}/messages:send";
    
    // Get access token from service account
    $accessToken = getAccessToken($serviceAccountPath);
    
    $message = [
        'message' => [
            'topic' => $topic,
            'data' => $data,
        ]
    ];
    
    $ch = curl_init($url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_POST, true);
    curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($message));
    curl_setopt($ch, CURLOPT_HTTPHEADER, [
        'Content-Type: application/json',
        "Authorization: Bearer {$accessToken}"
    ]);
    
    $response = curl_exec($ch);
    $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
    curl_close($ch);
    
    if ($httpCode >= 200 && $httpCode < 300) {
        echo "Successfully sent message to topic: " . $response . PHP_EOL;
        return json_decode($response, true);
    } else {
        echo "Error sending message to topic: " . $response . PHP_EOL;
        throw new Exception("FCM Error: " . $response);
    }
}

/**
 * Main function to demonstrate usage
 */
function main() {
    $serviceAccountPath = '';  // Path to your service account JSON file
    $projectId = '';           // Your Firebase project ID
    $topic = '';               // Topic name without /topics/ prefix
    $data = ['mail' => '', 'number' => ''];
    
    try {
        sendFCMMessageToTopic($serviceAccountPath, $projectId, $topic, $data);
        echo "Message sent successfully" . PHP_EOL;
    } catch (Exception $e) {
        echo "Error: " . $e->getMessage() . PHP_EOL;
    }
}

// Run the main function
main();