You can even configure your web server to process all your HTML files with PHP, and then there's really no way that users can tell what you have up your sleeve. (See: http://www.php .net/manual/en/introduction.php)
The best things in using PHP are that it is extremely simple for a newcomer, but offers many advanced features for a professional programmer. Don't be afraid reading the long list of PHP's features. You can jump in, in a short time, and start writing simple scripts in a few hours.
Almost anything. PHP is primarily focused on server-side scripting, so you can do anything a CGI program can do, such as collect form data, generate dynamic page content, or send and receive cookies. But PHP can do much more.
Server-side scripting: This is the most traditional and main target field for PHP. We need three things to make this work. The PHP parser (CGI or server module), a web server and a web browser. We need to run the web server, with a connected PHP installation. We can access the PHP program output with a web browser, viewing the PHP page through the server. All these can run on our home machine if we are just experimenting with PHP programming.
Command line scripting: We can make a PHP script to run it without any server or browser. ...