firebase_notification_curl.php

function sendNotifiction($title, $message){

		$header = array(
		    "authorization: key=YOUR_FIREBASE_KEY",
		    "content-type: application/json",
		 );

		$data = array
		(
			'title' => $title,
			'message' => $message,
 		);

		$body = array
		(
			'data' => $data,
			'to' => '/topics/test',
		);

		$curl = curl_init();

		curl_setopt_array($curl, array(
		  CURLOPT_URL => "https://fcm.googleapis.com/fcm/send",
		  CURLOPT_RETURNTRANSFER => true,
		  CURLOPT_ENCODING => "",
		  CURLOPT_MAXREDIRS => 10,
		  CURLOPT_TIMEOUT => 30,
		  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
		  CURLOPT_CUSTOMREQUEST => "POST",
		  CURLOPT_POSTFIELDS => json_encode($body),
		  CURLOPT_HTTPHEADER => $header,
		));

		$response = json_decode(curl_exec($curl));
		$err = curl_error($curl);
		$success = (isset($response->message_id));
		curl_close($curl);
		return $success;
	}