The name PHP did not always mean what it means today. According to PHP’s own documented history, the language began in 1994 when Rasmus Lerdorf created a set of tools to track visits to his online resume. He called them “Personal Home Page Tools,” and the abbreviation PHP originally stood for “Personal Home Page.”
As the tools grew into a real programming language, that name no longer fit. The early package was known as PHP/FI, and its name still carried “the implication of limited personal use.” When a rewritten version, PHP 3.0, was released in 1998, the project deliberately dropped that baggage.
The history page explains that PHP 3.0 “was renamed simply ‘PHP’, with the meaning becoming a recursive acronym - PHP: Hypertext Preprocessor.” A recursive acronym is one whose expansion refers back to itself, so the first letter of “PHP: Hypertext Preprocessor” is itself PHP.
The result is a small piece of programming trivia hiding inside one of the web’s most widely used languages: the same three letters were quietly redefined from a humble “personal home page” into a self-referential description of what the language actually does, preprocess hypertext.