What is the difference between php php3 and phtml?

PHP, PHP3, and PHTML refer to different versions and contexts of the PHP programming language. PHP is the current and widely used version, while PHP3 is an older version that introduced many features but is no longer supported. PHTML is a file extension typically used for PHP files, indicating that the file contains PHP code, while .php is the more common extension today. In summary, the key differences lie in versioning and file naming conventions.