Push Notification Using Firebase

function wc_push_notification($title, $message, $token){

    define( 'API_ACCESS_KEY', 'AIzaSyAWmIMxm6uCGOilk2TNCAAYXBVrDXT0k74'); //Server API KEY(usually you can find it by settings > project setting > cloudmessaging)
    $msg = array('body'  => $message,'title' => $title);
    $fields = array('to'        => $token,'notification'  => $msg);

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

    $ch = curl_init();
    curl_setopt( $ch,CURLOPT_URL, 'https://fcm.googleapis.com/fcm/send' );
    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 );
}

Usage:

wc_push_notification('Push Notification Title', 'Push Notification Body', 'DEVICE_TOKEN');