This document outlines the simple steps to design a custom PHP website or application, including defining requirements and scope, creating a database structure, developing the front end, and implementing back-end functionality. It recommends determining features, pages, and interactions; designing effective data organization; and connecting a PHP back-end to the database to handle data and user input. The document also provides contact information for Smartinfosys.net, a company that specializes in website design, development, and SEO services.