A HTML CSS PHP developer designs, builds, and maintains websites. They use HTML (HyperText Markup Language) to create the structure and content of web pages, CSS (Cascading Style Sheets) to control the presentation, style, and layout, and PHP (Hypertext Preprocessor) for server-side scripting to make websites dynamic and interactive. They ensure websites are responsive, user-friendly, and accessible across various devices. They also handle website troubleshooting and performance optimization. Additionally, they may work with databases using PHP and SQL, integrate APIs, and collaborate with teams to implement user-facing elements and server-side logic.