This extension provides formatting for the HTML code in PHP files. This way this works is this extension runs right before the save action which triggers any other registered PHP formatting extensions ...

A code editor is a software application that allows you to write, edit, and manage HTML files. Code editors offer features such as syntax highlighting, auto-completion, indentation, code folding ...

They usually have features like syntax highlighting, code completion, formatting, validation, and debugging, as well as support for other web languages like CSS, JavaScript, and PHP.