How to design a simple and reusable form validation class in PHP?

Question

We all know, nearly in all web apps, we need this functionality. To validate data coming from form inputs. What would be a good approach to design such class.

Answer 1

https://www.inmotionhosting.com/support/edu/website-design/using-php-and-mysql/how-to-create-a-custom-php-contact-form