I have successfully activated the SMS Subscription service. User can send send with special keywork and can subscribe to SMS Subscription.
But SMS cannot be send to SMS subscriber. Whenever “Send this message to all members” Send button is clicking its showing error. Please see the screencast https://techtun.es/Jl43SS
After checking the php log its showing the following error
[12-Jun-2019 08:23:21] WARNING: [pool www] child 30690 said into stderr: “[12-Jun-2019 14:23:21 Asia/Dhaka] PHP Fatal error: Uncaught Error:  operator not supported for strings in /var/www/t-sms-app/plugin/feature/sms_subscribe/sms_subscribe.php:727”