Trying send push notification throws an exception? - php

Question

I'm trying create a PHP class to send Push Notification. When I try send push doesn't works an throws an exception of syntax error and I can't find this error. I'm using PHP 5.3.28.
How could I solve it ?
Pusher
<?php
class Pusher{
const GOOGLE_GCM_URL = 'https://android.googleapis.com/gcm/send';
private $apiKey;
private $proxy;
private $output;
public function __construct($apiKey, $proxy = null)
{
$this->apiKey = $apiKey;
$this->proxy = $proxy;
}
/**
* #param string|array $regIds
* #param string $data
* #throws \Exception
*/
public function notify($regIds, $data)
{
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, self::GOOGLE_GCM_URL);
if (!is_null($this->proxy)) {
curl_setopt($ch, CURLOPT_PROXY, $this->proxy);
}
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, $this->getHeaders());
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt($ch, CURLOPT_POSTFIELDS, $this->getPostFields($regIds, $data));
$result = curl_exec($ch);
if ($result === false) {
throw new \Exception(curl_error($ch));
}
curl_close($ch);
$this->output = $result;
}
/**
* #return array
*/
public function getOutputAsArray()
{
return json_decode($this->output, true);
}
/**
* #return object
*/
public function getOutputAsObject()
{
return json_decode($this->output);
}
private function getHeaders(){
return [
'Authorization: key=' . $this->apiKey,
'Content-Type: application/json'
];
}
private function getPostFields($regIds, $data){
$fields = [
'registration_ids' => is_string($regIds) ? [$regIds] : $regIds,
'data' => is_string($data) ? ['message' => $data] : $data,
];
return json_encode($fields, JSON_HEX_TAG | JSON_HEX_APOS | JSON_HEX_QUOT | JSON_HEX_AMP | JSON_UNESCAPED_UNICODE);
}
}
Exception
Fatal Error
Error: syntax error, unexpected '['
File: /app/Plugin/Push/Pusher.php
Line: 60
At line 60 have
private function getHeaders(){
return [
'Authorization: key=' . $this->apiKey,
'Content-Type: application/json'
];
}