Why PHP script is not workig in a web browser?

We have all seen many question on StackOverflow that are founded upon the idea that PHP works like Javascript. Where the person clearly does not understand that PHP is a Preproccessor and only works before the page is sent out. A clear example of this is in the following code, where `runCommand()` will not run when the user presses the button. ``` <a href="<?php runCommand(); ?>">Click Me!</a> ``` as it would in Javascript ``` <a href="javascript:runCommand();">Click Me!</a> ``` I've seen many questions like this that are from new people that just simply don't realize 'how' PHP works. My question is: Where is a great resource that explains how PHP works?. I want to be able to redirect people to a page that can get them going on the correct track and know what being a Preproccessor means. (This also allows me to be lazy and not have to write an explanation every time it comes up, but don't tell anyone!) If you don't know of a place that describes this well, feel free to provide your own interpretation. As Carl Smotricz points out, there is a part of PHP that can be used outside of the browser. But I'm mainly talking about in a Apache enviorment where a user requests a web page, and expects to get something back, usually in HTML.