diff --git a/composer.json b/composer.json
index 8500848..03058e7 100644
--- a/composer.json
+++ b/composer.json
@@ -5,14 +5,12 @@
     "license": "MIT",
     "require": {
         "php": ">=7.1",
-        "psr/cache": "^1|^2|^3",
-        "google/auth": "^1.21.0",
+        "psr/cache": "^1.0||^2.0||^3.0",
+        "google/auth": "^1.29.0",
         "guzzlehttp/guzzle": "^7.4.2",
         "firebase/php-jwt": "^6.4"
     },
-    "require-dev": {
-	},
-
+    "require-dev": {},
     "autoload": {
         "psr-4": {
             "Plokko\\Firebase\\": "src/"
@@ -23,4 +21,4 @@
             "Plokko\\Firebase\\Tests\\": "tests/"
         }
     }
-}
+}
\ No newline at end of file
diff --git a/src/FCM/Message.php b/src/FCM/Message.php
index d1286eb..e58bfac 100644
--- a/src/FCM/Message.php
+++ b/src/FCM/Message.php
@@ -1,4 +1,5 @@
 <?php
+
 namespace Plokko\Firebase\FCM;
 
 use GuzzleHttp\Exception\GuzzleException;
@@ -24,7 +25,8 @@
  * @property ApnsConfig $apns Apple Push Notification Service specific options.
  * @property Target $target
  */
-class Message implements JsonSerializable {
+class Message implements JsonSerializable
+{
     private
         /**@var string**/
         $name,
@@ -48,9 +50,9 @@ function __construct()
 
     function __get($name)
     {
-        if(!$this->{$name}){
+        if (!$this->{$name}) {
             //Lazy creation
-            switch($name){
+            switch ($name) {
                 case 'data':
                     $this->data = new Data();
                     break;
@@ -72,50 +74,52 @@ function __get($name)
         return $this->{$name};
     }
 
-    function __set($k,$v){
-        switch($k){
+    function __set($k, $v)
+    {
+        switch ($k) {
             case 'data':
-                $this->data = $v==null||$v instanceof Data?$v:new Data($v);
+                $this->data = $v == null || $v instanceof Data ? $v : new Data($v);
                 return;
             case 'notification':
-                if($v!==null&& !$v instanceof Notification )
+                if ($v !== null && !$v instanceof Notification)
                     break;
                 $this->notification = $v;
                 return;
             case 'android':
-                if($v!==null && !$v instanceof AndroidConfig)
+                if ($v !== null && !$v instanceof AndroidConfig)
                     break;
                 $this->android = $v;
                 return;
             case 'webpush':
-                if($v!==null && !$v instanceof WebpushConfig)
+                if ($v !== null && !$v instanceof WebpushConfig)
                     break;
                 $this->webpush = $v;
                 return;
             case 'apns':
-                if($v!==null && !$v instanceof ApnsConfig )
+                if ($v !== null && !$v instanceof ApnsConfig)
                     break;
                 $this->apns = $v;
                 return;
             case 'target':
-                if($v!==null && !$v instanceof Target)
+                if ($v !== null && !$v instanceof Target)
                     break;
                 $this->target = $v;
                 return;
             default:
-
         }
-        throw new UnexpectedValueException('Invalid value type for propriety '.$k);
+        throw new UnexpectedValueException('Invalid value type for propriety ' . $k);
     }
 
-    function setTarget(Target $target){
+    function setTarget(Target $target)
+    {
         $this->target = $target;
     }
 
 
-    function getPayload(){
-        if(!$this->target){
-            throw new UnexpectedValueException('FCMMEssage target not specified!','TARGET_NOT_SPECIFIED');
+    function getPayload()
+    {
+        if (!$this->target) {
+            throw new UnexpectedValueException('FCMMEssage target not specified!', 'TARGET_NOT_SPECIFIED');
         }
 
         $data = array_filter([
@@ -125,7 +129,7 @@ function getPayload(){
             'webpush'       => $this->webpush,
             'apns'          => $this->apns,
         ]);
-        return array_merge($data,$this->target->jsonSerialize());
+        return array_merge($data, $this->target->jsonSerialize());
     }
 
     /**
@@ -134,9 +138,10 @@ function getPayload(){
      * @throws FcmErrorException
      * @throws GuzzleException
      */
-    public function send(Request $request){
+    public function send(Request $request)
+    {
         $name = $request->submit($this);
-        if(!$request->validate_only)
+        if (!$request->validate_only)
             $this->name = $name;
     }
 
@@ -147,16 +152,17 @@ public function send(Request $request){
      * @throws GuzzleException
      * @throws FcmErrorException
      */
-    public function validate(Request $request){
+    public function validate(Request $request)
+    {
         $request = clone $request;
-        $request->validate_only=true;
+        $request->validate_only = true;
 
         $request->submit($this);
 
         return true;
     }
 
-    public function jsonSerialize()
+    public function jsonSerialize(): mixed
     {
         $data = array_filter([
             'name'          => $this->name,
@@ -167,7 +173,7 @@ public function jsonSerialize()
             'apns'          => $this->apns,
         ]);
 
-        return $this->target?array_merge($data,$this->target->jsonSerialize()):$data;
+        return $this->target ? array_merge($data, $this->target->jsonSerialize()) : $data;
     }
 
     function __toString()
@@ -179,7 +185,8 @@ function __toString()
      * Tells if the request was already submitted (if it has an id)
      * @return bool
      */
-    function isSubmitted(){
+    function isSubmitted()
+    {
         return !!$this->name;
     }
-}
\ No newline at end of file
+}
diff --git a/src/FCM/Message/AndroidConfig.php b/src/FCM/Message/AndroidConfig.php
index aa02e87..aea5535 100644
--- a/src/FCM/Message/AndroidConfig.php
+++ b/src/FCM/Message/AndroidConfig.php
@@ -1,4 +1,5 @@
 <?php
+
 namespace Plokko\Firebase\FCM\Message;
 
 use InvalidArgumentException;
@@ -19,8 +20,8 @@
 class AndroidConfig implements JsonSerializable
 {
     const
-        PRIORITY_NORMAL='normal',
-        PRIORITY_HIGH='high';
+        PRIORITY_NORMAL = 'normal',
+        PRIORITY_HIGH = 'high';
 
 
     private
@@ -39,19 +40,21 @@ class AndroidConfig implements JsonSerializable
      * @param string $ttl Ttl expressed as string (ex: '3.5s')
      * @return $this
      */
-    function ttl($ttl){
-        $this->ttl=$ttl;
+    function ttl($ttl)
+    {
+        $this->ttl = $ttl;
         return $this;
     }
 
-    function __get($k){
-        switch($k){
+    function __get($k)
+    {
+        switch ($k) {
             case 'data':
-                if(!$this->data)
+                if (!$this->data)
                     $this->data = new Data();
                 break;
             case 'notification':
-                if(!$this->notification)
+                if (!$this->notification)
                     $this->notification = new AndroidNotification();
                 break;
             default:
@@ -59,14 +62,15 @@ function __get($k){
         return $this->{$k};
     }
 
-    function __set($k,$v){
-        switch($k){
+    function __set($k, $v)
+    {
+        switch ($k) {
             case 'priority':
                 $this->setPriority($v);
                 break;
             default:
         }
-        $this->{$k}=$v;
+        $this->{$k} = $v;
     }
 
     /**
@@ -74,28 +78,31 @@ function __set($k,$v){
      * @throws InvalidArgumentException
      * @return AndroidConfig
      */
-    function setPriority($p){
-        switch ($p){
+    function setPriority($p)
+    {
+        switch ($p) {
             default:
                 throw new InvalidArgumentException('Invalid Android message priority!');
             case self::PRIORITY_NORMAL:
             case self::PRIORITY_HIGH:
-                $this->priority=$p;
+                $this->priority = $p;
         }
         return $this;
     }
 
-    function setPriorityHigh(){
+    function setPriorityHigh()
+    {
         $this->priority = self::PRIORITY_HIGH;
         return $this;
     }
 
-    function setPriorityNormal(){
+    function setPriorityNormal()
+    {
         $this->priority = self::PRIORITY_NORMAL;
         return $this;
     }
 
-    public function jsonSerialize()
+    public function jsonSerialize(): mixed
     {
         return array_filter([
             'collapse_key'  => $this->collapse_key,
diff --git a/src/FCM/Message/AndroidNotification.php b/src/FCM/Message/AndroidNotification.php
index 201f8f5..eac5c92 100644
--- a/src/FCM/Message/AndroidNotification.php
+++ b/src/FCM/Message/AndroidNotification.php
@@ -1,4 +1,5 @@
 <?php
+
 namespace Plokko\Firebase\FCM\Message;
 
 use JsonSerializable;
@@ -34,10 +35,16 @@ class AndroidNotification implements JsonSerializable
         /**@var array**/
         $title_loc_args;
 
-    function __get($k){return $this->{$k};}
-    function __set($k,$v){$this->{$k}=$v;}
+    function __get($k)
+    {
+        return $this->{$k};
+    }
+    function __set($k, $v)
+    {
+        $this->{$k} = $v;
+    }
 
-    public function jsonSerialize()
+    public function jsonSerialize(): mixed
     {
         return array_filter([
             'title' => $this->title,
@@ -53,4 +60,4 @@ public function jsonSerialize()
             'title_loc_args' => $this->title_loc_args,
         ]);
     }
-}
\ No newline at end of file
+}
diff --git a/src/FCM/Message/Apns/ApnsAlert.php b/src/FCM/Message/Apns/ApnsAlert.php
index a4ff717..efdf646 100644
--- a/src/FCM/Message/Apns/ApnsAlert.php
+++ b/src/FCM/Message/Apns/ApnsAlert.php
@@ -37,7 +37,7 @@ class ApnsAlert implements JsonSerializable
         /** @var string **/
         $launch_image;
 
-    function __construct($title='',$body='')
+    function __construct($title = '', $body = '')
     {
         $this->title = $title;
         $this->body = $body;
@@ -50,10 +50,10 @@ function __get($k)
 
     function __set($k, $v)
     {
-        $this->{$k}=$v;
+        $this->{$k} = $v;
     }
 
-    public function jsonSerialize()
+    public function jsonSerialize(): mixed
     {
         return array_filter([
             'title' => $this->title,
@@ -66,4 +66,4 @@ public function jsonSerialize()
             'launch-image' => $this->launch_image,
         ]);
     }
-}
\ No newline at end of file
+}
diff --git a/src/FCM/Message/Apns/ApnsPayload.php b/src/FCM/Message/Apns/ApnsPayload.php
index 7a8d80f..17a123d 100644
--- a/src/FCM/Message/Apns/ApnsPayload.php
+++ b/src/FCM/Message/Apns/ApnsPayload.php
@@ -1,4 +1,5 @@
 <?php
+
 namespace Plokko\Firebase\FCM\Message\Apns;
 
 use JsonSerializable;
@@ -17,30 +18,30 @@ class ApnsPayload implements JsonSerializable
         $aps;
     private
         /**@var array Custom data for app (acme)**/
-        $app_data=[];
+        $app_data = [];
 
     function __get($k)
     {
-        if($k==='aps'){
-            if(!$this->aps)
+        if ($k === 'aps') {
+            if (!$this->aps)
                 $this->aps = new ApsData();
             return $this->aps;
         }
-        return array_key_exists($k,$this->app_data)?$this->app_data[$k]:null;
+        return array_key_exists($k, $this->app_data) ? $this->app_data[$k] : null;
     }
 
     function __set($k, $v)
     {
-        if($k==='aps'){
+        if ($k === 'aps') {
             throw new \InvalidArgumentException('aps is a reserved keyword');
         }
         $this->app_data[$k] = $v;
     }
 
-    public function jsonSerialize()
+    public function jsonSerialize(): mixed
     {
-        return array_filter(array_merge($this->app_data,[
-            'aps'=>$this->aps,
+        return array_filter(array_merge($this->app_data, [
+            'aps' => $this->aps,
         ]));
     }
-}
\ No newline at end of file
+}
diff --git a/src/FCM/Message/Apns/ApsData.php b/src/FCM/Message/Apns/ApsData.php
index 7a7510e..f356db0 100644
--- a/src/FCM/Message/Apns/ApsData.php
+++ b/src/FCM/Message/Apns/ApsData.php
@@ -28,7 +28,7 @@ class ApsData implements JsonSerializable
         /** @var string */
         $thread_id;
 
-    public function jsonSerialize()
+    public function jsonSerialize(): mixed
     {
         return array_filter([
             'alert' => $this->alert,
@@ -40,4 +40,4 @@ public function jsonSerialize()
             'thread-id' => $this->thread_id,
         ]);
     }
-}
\ No newline at end of file
+}
diff --git a/src/FCM/Message/Data.php b/src/FCM/Message/Data.php
index 8805fc2..fe70a2b 100644
--- a/src/FCM/Message/Data.php
+++ b/src/FCM/Message/Data.php
@@ -1,19 +1,22 @@
 <?php
+
 namespace Plokko\Firebase\FCM\Message;
 
 use ArrayAccess;
 use JsonSerializable;
 
-class Data implements ArrayAccess,JsonSerializable
+class Data implements ArrayAccess, JsonSerializable
 {
     private
-        $data=[];
+        $data = [];
 
-    function __construct($data=[]){
+    function __construct($data = [])
+    {
         $this->data = $data;
     }
 
-    function get($k){
+    function get($k)
+    {
         return $this->data[$k];
     }
 
@@ -22,51 +25,58 @@ function get($k){
      * @param $v
      * @return $this
      */
-    function set($k,$v){
-        $this->data[$k]=$v;
+    function set($k, $v)
+    {
+        $this->data[$k] = $v;
         return $this;
     }
 
 
 
-    function fill(array $data){
-        $this->data=$data;
+    function fill(array $data)
+    {
+        $this->data = $data;
     }
-    function clear(){
-        $this->data=[];
+    function clear()
+    {
+        $this->data = [];
     }
 
-    function __set($k,$v){
-        $this->set($k,$v);
+    function __set($k, $v)
+    {
+        $this->set($k, $v);
     }
-    function __get($k){
+    function __get($k)
+    {
         return $this->get($k);
     }
 
-    public function offsetExists($offset)
+    public function offsetExists($offset): bool
     {
         return isset($this->data[$offset]);
     }
 
-    public function offsetGet($offset)
+    public function offsetGet($offset): mixed
     {
         return $this->data[$offset];
     }
 
-    public function offsetSet($offset, $value)
+    public function offsetSet($offset, $value): void
     {
         $this->data[$offset] = $value;
     }
 
-    public function offsetUnset($offset)
+    public function offsetUnset($offset): void
     {
         unset($this->data[$offset]);
     }
 
 
-    public function jsonSerialize()
+    public function jsonSerialize(): mixed
     {
         // Force a string : string array
-        return array_map(function($v){return ''.$v;},$this->data);
+        return array_map(function ($v) {
+            return '' . $v;
+        }, $this->data);
     }
-}
\ No newline at end of file
+}
diff --git a/src/FCM/Message/Notification.php b/src/FCM/Message/Notification.php
index 2eb882a..baef842 100644
--- a/src/FCM/Message/Notification.php
+++ b/src/FCM/Message/Notification.php
@@ -1,4 +1,5 @@
 <?php
+
 namespace Plokko\Firebase\FCM\Message;
 
 use JsonSerializable;
@@ -16,29 +17,31 @@ class Notification implements JsonSerializable
         /**@var string The notification's body text.*/
         $body;
 
-    function __construct($title='',$body='')
+    function __construct($title = '', $body = '')
     {
         $this->title = $title;
         $this->body = $body;
     }
 
 
-    function setTitle($title){
+    function setTitle($title)
+    {
         $this->title = $title;
         return $this;
     }
 
-    function setBody($body){
+    function setBody($body)
+    {
         $this->body = $body;
         return $this;
     }
 
 
-    public function jsonSerialize()
+    public function jsonSerialize(): mixed
     {
         return [
             'title' => $this->title,
             'body'  => $this->body,
         ];
     }
-}
\ No newline at end of file
+}
diff --git a/src/FCM/Message/WebPushNotification.php b/src/FCM/Message/WebPushNotification.php
index 5ed3df9..5d76871 100644
--- a/src/FCM/Message/WebPushNotification.php
+++ b/src/FCM/Message/WebPushNotification.php
@@ -1,4 +1,5 @@
 <?php
+
 namespace Plokko\Firebase\FCM\Message;
 
 use JsonSerializable;
@@ -18,7 +19,7 @@ class WebPushNotification implements JsonSerializable
         /**@var string**/
         $icon;
 
-    public function jsonSerialize()
+    public function jsonSerialize(): mixed
     {
         return array_filter([
             'title' => $this->title,
@@ -26,4 +27,4 @@ public function jsonSerialize()
             'icon'  => $this->icon,
         ]);
     }
-}
\ No newline at end of file
+}
diff --git a/src/FCM/Message/WebpushConfig.php b/src/FCM/Message/WebpushConfig.php
index e9559b9..09da6b5 100644
--- a/src/FCM/Message/WebpushConfig.php
+++ b/src/FCM/Message/WebpushConfig.php
@@ -32,13 +32,13 @@ class WebpushConfig implements JsonSerializable
     function __get($k)
     {
         if ($k === 'notification') {
-            if(!$this->notification) {
+            if (!$this->notification) {
                 $this->notification = new WebPushNotification();
             }
         }
 
         if ($k === 'fcm_options') {
-            if(!$this->fcm_options) {
+            if (!$this->fcm_options) {
                 $this->fcm_options = new WebpushFcmOptions();
             }
         }
@@ -48,10 +48,10 @@ function __get($k)
 
     function __set($k, $v)
     {
-        $this->{$k}=$v;
+        $this->{$k} = $v;
     }
 
-    public function jsonSerialize()
+    public function jsonSerialize(): mixed
     {
         return array_filter([
             'headers'        => $this->headers,
@@ -60,4 +60,4 @@ public function jsonSerialize()
             'fcm_options'   => $this->fcm_options,
         ]);
     }
-}
\ No newline at end of file
+}
diff --git a/src/FCM/Message/WebpushFcmOptions.php b/src/FCM/Message/WebpushFcmOptions.php
index 7f46e89..b459d0b 100644
--- a/src/FCM/Message/WebpushFcmOptions.php
+++ b/src/FCM/Message/WebpushFcmOptions.php
@@ -24,13 +24,13 @@ function __get($k)
 
     function __set($k, $v)
     {
-        $this->{$k}=$v;
+        $this->{$k} = $v;
     }
 
-    public function jsonSerialize()
+    public function jsonSerialize(): mixed
     {
         return array_filter([
             'link' => $this->link,
         ]);
     }
-}
\ No newline at end of file
+}
diff --git a/src/FCM/Targets/Target.php b/src/FCM/Targets/Target.php
index 415dc3c..d633a1d 100644
--- a/src/FCM/Targets/Target.php
+++ b/src/FCM/Targets/Target.php
@@ -1,5 +1,7 @@
 <?php
+
 namespace Plokko\Firebase\FCM\Targets;
+
 use JsonSerializable;
 use ReflectionClass;
 
@@ -21,8 +23,8 @@ final function __construct($value)
         $this->value = $value;
     }
 
-    public function jsonSerialize(){
-        return [ strtolower((new ReflectionClass($this))->getShortName()) => $this->value ];
+    public function jsonSerialize(): mixed
+    {
+        return [strtolower((new ReflectionClass($this))->getShortName()) => $this->value];
     }
-
-}
\ No newline at end of file
+}
diff --git a/src/IO/Reference.php b/src/IO/Reference.php
index 864ef7d..9f5e8d0 100644
--- a/src/IO/Reference.php
+++ b/src/IO/Reference.php
@@ -1,4 +1,5 @@
 <?php
+
 namespace Plokko\Firebase\IO;
 
 use JsonSerializable;
@@ -9,12 +10,12 @@ class Reference implements JsonSerializable
         $db,
         $path,
 
-        $data=null;
+        $data = null;
 
-    function __construct(Database $db,$path)
+    function __construct(Database $db, $path)
     {
         $this->db = $db;
-        $this->path=trim($path,'/');
+        $this->path = trim($path, '/');
     }
 
     /**
@@ -22,62 +23,73 @@ function __construct(Database $db,$path)
      * @param $path string optional sub path to concatenate
      * @return string
      */
-    function getPath($path=''){
-        return $this->path.'/'.trim($path,'/');
+    function getPath($path = '')
+    {
+        return $this->path . '/' . trim($path, '/');
     }
 
-    private function getData(){
-        if(!$this->data){
-            $this->data=$this->get();
+    private function getData()
+    {
+        if (!$this->data) {
+            $this->data = $this->get();
         }
         return $this->data;
     }
 
-    public function fetch(){
-        $this->data=$this->get();
+    public function fetch()
+    {
+        $this->data = $this->get();
     }
 
     /**
      * @param $path
      * @return Reference
      */
-    function getReference($path){
-        return new Reference($this->db,$this->path.'/'.$path);
+    function getReference($path)
+    {
+        return new Reference($this->db, $this->path . '/' . $path);
     }
 
-    function get($path=''){
+    function get($path = '')
+    {
         return $this->db->get($this->getPath($path));
     }
 
-    function set($value){
-        $this->db->set($this->path,$value);
+    function set($value)
+    {
+        $this->db->set($this->path, $value);
     }
 
-    function update($path,$value){
-        $this->db->update($this->getPath($path),$value);
+    function update($path, $value)
+    {
+        $this->db->update($this->getPath($path), $value);
     }
 
-    function delete($path=''){
+    function delete($path = '')
+    {
         $this->db->delete($this->getPath($path));
     }
 
 
 
-    function __get($k){
+    function __get($k)
+    {
         $this->getData()[$k];
     }
 
-    function __set($path,$value){
-        $this->update($this->getPath($path),$value);
+    function __set($path, $value)
+    {
+        $this->update($this->getPath($path), $value);
     }
 
 
-    function toArray(){
+    function toArray()
+    {
         return $this->getData();
     }
 
-    public function jsonSerialize()
+    public function jsonSerialize(): mixed
     {
         return $this->toArray();
     }
-}
\ No newline at end of file
+}
diff --git a/src/RemoteConfig/Models/RemoteConfig.php b/src/RemoteConfig/Models/RemoteConfig.php
index 6a2bec6..b0904e1 100644
--- a/src/RemoteConfig/Models/RemoteConfig.php
+++ b/src/RemoteConfig/Models/RemoteConfig.php
@@ -1,4 +1,5 @@
 <?php
+
 namespace Plokko\Firebase\RemoteConfig\Models;
 
 use JsonSerializable;
@@ -9,11 +10,11 @@ class RemoteConfig implements JsonSerializable
         $conditions,
         $parameters;
 
-    public function jsonSerialize()
+    public function jsonSerialize(): mixed
     {
         return [
             'conditions' => $this->conditions,
             'parameters' =>  $this->parameters,
         ];
     }
-}
\ No newline at end of file
+}