如何使用json对象数组生成有效的json输出

I created a mySQL database with phpMyAdmin in my local server. In this database I stored the names and the location of my friends (along with an id as a primary key for the database). I wrote and run the following php script to retrieve these data from the database and project them on my local web server (XAMPP):I created a mySQL database with phpMyAdmin in m