The "Php 4 developer's guide" covers various topics related to building and working with PHP4, a programming language commonly used for web development. It includes chapters on installing PHP4, understanding the language, handling forms and cookies, working with files and databases, managing sessions and application state, implementing authentication, ensuring browser compatibility, debugging code, reusing code, separating HTML from PHP, creating template-based and database-driven websites, generating static HTML pages, and developing e-commerce websites. The guide aims to help developers learn how to effectively use PHP4 for creating dynamic and interactive web applications.