I want to make data entry form which inserts data to MySQL.

Select (Dropdown) from List A --- Values of dropdown to be populate from database A
Select (Dropdown) from List B ---- Values of dropdown to be populated from database B
and so on
Select (Dropdown) from List N ---- Values of dropdown to be populated from database n


Data entered to List C

If you have attempted something on your own, post them here. If you want to get some idea, i will provide you some basic idea to start with. If you want to obtain data from your database, you must connect to the database in PHP. Search on these commands to understand how the database is connected.


Next is to create your form where the dropdown list would show the data from the database. To do this, make sure the connection is done right. Data can be fetched in a numeric manner or in an associative array. Search how to do this in database. As you are selecting a value from the dropdown list, you can assign the value to a new variable that can be passed to List C after you have pressed submit button.

This is a basic idea i can provide with. Good Luck :)