How to separate form and validation into different files?

Question

I'm trying out to make a home page where user can input fields. Then I want it to go to the validation file to process validation.
After that, if there is empty fields it will go back to home page and notify user that it is required field.
If ever the input is not valid, it will also notify the user going back again in the home.
However, if the input is valid, it will display the result in home page.

I'm just a newbie, and stuck in this matter.

Thanks for the suggestions and comments in advance. :)

Answer 1

Here’s a simple tutorial for forms and validation from w3schools. This should give you a better idea of what should be going on.

https://www.w3schools.com/php/php_forms.asp