when try to install sentry 2 with composer it will installed very well. but how can use in existing PHP project thanks in advance.
methods with that of sentry's.
It would be good if you follow the Sentinel documentaion. It's a good one for beginners. Sentinel 2.0
Also a lot depends on the PHP framework you are using for your backend. If you are using something big like zend, yii etc. they already have a pretty good authentication system of their own.
If you are using a light weight framework suppose Slim then there the documentation will guide you pretty well to set it up. Also there are various blogs online explaining the same.