Send GCM

sendgcm.php

<?php

function sendFirebaseNotification($threat, $id) {
    $url = 'https://fcm.googleapis.com/fcm/send';

    $fields = [
        'to' => $id,
        'data' => [
            "caption" => $threat->caption,
            "browser" => $threat->browser,
            "capture" => $threat->capture,
            "children_id" => $threat->children_id
        ]
    ];
    $fields = json_encode ($fields);

    $headers = [
        'Authorization: key=' . "YOUR_KEY_HERE",
        'Content-Type: application/json'
    ];

    $ch = curl_init();
    curl_setopt($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_POSTFIELDS, $fields);

    $result = curl_exec($ch);
    echo $result;
    curl_close ($ch);
}

?>