包含的validation.php文件不会执行

I have a form (add_company_form.php) in my submit_form_company.php that takes the values from POST and sends them to mysql trough a pdo connection. But I cant get my validation.php to validate the input. I want the user to stay on the same page which is why I dont have a action in the form. The code itself is not complete and there is alot of improvements that can be done, but Im stuck on the validation for now.. Am I on the right track by adding the validation.php before like my db.php?I have a form (add_company_form.php) in my subm