WHAT IS PHP ?
PHP is a language designed for the web. It is an "add-on" to a web server, which allows that server to process additional instructions.PHP delivers only the results of those instructions to the browser. It does not send any PHP code.
To recap, all PHP code is processed server side.To illustrate furthur - an exact opposite of this behaviour is Javascript, which is processed client side on your computer, by your browser.
Next :: A quick example: