PHP coding standards

I usually try and follow the standards that are set by the language's core libraries.... oh wait.

Seriously through - you should try and follow the MVC pattern in any web application as it is pretty much standard practice regardless of language. In PHP this can be achieved in a quick-and-dirty way by treating index.php as your controller and separating data logic and presentation by file. This small step will at least let you move your code to a full featured framework when and if you choose.

Combining programming code and output data (including HTML) is IMHO a very bad idea. Most of the PHP gurus I know use a template engine such as Smarty to help keep the two things separate.

Use a template engine when you can. If you haven't learned one, or don't want the overhead (which is minimal), use practices that cause you to have quick-and-dirty templating:

• Functions that do not display anything have no place in a file that does display something.
• Print variables, not HTML. Whenever outputting HTML, break out of the PHP and write HTML with print statements to handle any small details that are needed (actions for forms, IDs for controls, etc.).
• Remember, when you include a file that breaks out of the PHP to print content, that will be treated the same as if you do it in the main file. So you can create simple templates that just included PHP files, and those files will print variables in the right places. Your index.php (or whatever) does all the real work, but all the display is done by the secondary "template".

Many PHP tutorials intermix logic and display code. It took me years to break the bad habits that encouraged in me. In my experience you can't separate things too much in PHP, and entropy will pull you towards intermixed code if you don't fight it.

There's really not a single, common standard for these things. Most languages are more restrictive than PHP in this sense.

In the later years, a lot of so-called frameworks have emerged, and amongst other things they define a set of rules for everything from naming over where to place files and to which style your code should follow. There are several frameworks around, so you can't really pick one and call it the standard. However, most frameworks have a subset of commonality. For example, most follows some variant of the PEAR Coding Standards.