A lot of missing parts?
Note: Actually no. You missed that, this is a quick guide. This is for who understands the basics of Laravel and Firebase Push Notification. So the people who know the basics can join the missing parts.
# Answer to 1: No need
# Answer to 2: Answered in the above note
# Answer to 3: Answered in the above note
# Answer to 4: If you have read the post properly you would see the server key is used in UserController.php. Alas! you don't have enough time. Please have time to read the UserController.php (line 14) and .env.
Why I put the single key in .env? Okay. If you have knowledge of deployment to the UAT and PROD server, you would know why I had used it. For PROD and UAT, there must be different keys. To change this key easily at the time of deployment, it is a good practice to put any variable type things in .env file. I guess you understand now.
# Answer to 5: As mentioned in the above note. you need clear understandings of firebase push notification. db is not needed for push notification.
# Answer to 6: As mentioned in the above note. You need clear understandings of firebase push notification. How can you send push notification to anyone without knowing his device token? That function is used for that. Look at home.blade.php, line 82.
# Answer to 7: Look at the .env file and UserController.php (line 14).
# Answer to 8: Completely working for other people. It would work for you too if you have proper knowledge of development, laravel, and firebase.
Advice: 1. Learn Larvel basics 2. Learn firebase 3. Medium is free of cost writing space. Here, people write to help others. Someone like you does not appreciate the writing. It's very disappointing. Try to appreciate others first and then respond.