Javascript + selector + Database?

Question

PHP

There are 2 selectors:
1) Countries
2) Cities
There are two tables in Mysql:
1) Countries, each with its own unique ID
2) Cities that are related to countries by ID
Now, how to unload them from the database into selectors?

Answer 1

In the first country selector, by changing, you make an Ajax query to the city table, filtering by country id, insert the received data into the second select