How to use select tag in html to choose specific sqlite3 queries with php?

one text

Solution:

Your select name is chooseCountry while you're looking for $_POST['formCountry']

You should update your switch to

switch ($_POST['chooseCountry']){

Furthermore the isset function only returns booleans, true or false. You can not use it in the switch. If you want to avoid warnings, you need to add an if before the switch

if(isset($_POST['chooseCountry'])) {
    switch ($_POST['chooseCountry']){
        // CODE
    }
}