Update readme

Author: mhh1422

src/ElasticSessionStore.php

@@ -46,7 +46,7 @@ public static function putMapping() {
                     'updated' => ['type' => 'date'],
                     'data' => ['type' => 'string', 'index' => 'no'],
                 ],
-                '_ttl' => (!!$ttl ? ['enabled' => true, 'default' => $ttl? : '30m'] : ['enabled' => false])
+                '_ttl' => ($ttl ? ['enabled' => true, 'default' => $ttl? : '30m'] : ['enabled' => false])
             ]
         ];
         $client->indices()->putMapping($mappingParams);
@@ -77,7 +77,7 @@ public function write($sessionId, $sessionData) {
         $updatedTs = Carbon::now()->toIso8601String();
         $createdTs = array_key_exists($sessionId, $this->_cache) ? $this->_cache[$sessionId]->created : $updatedTs;
         $ttl = $this->getTTL();
-        static::create(['data' => $sessionData, 'created' => $createdTs, 'updated' => $updatedTs, '_ttl' => $ttl], $sessionId, ["api" => "index"]);
+        static::create(['data' => $sessionData, 'created' => $createdTs, 'updated' => $updatedTs] + ($ttl ? ['_ttl' => $ttl] : []), $sessionId, ["api" => "index"]);
     }
 
     public function destroy($sessionId) {
@@ -99,7 +99,7 @@ public function type() {
     protected function getTTL() {
         $ttl = config('session.lifetime', 30);
         $ttl.=$ttl ? 'm' : '';
-        return $ttl;
+        return !!$ttl ? $ttl : false;
     }
 
 }