Just like any language, developers can write code in PHP that ranges in quality from truly awful to very good. Learn good programming habits that can help you bridge the productivity gap. [...] Bad coding habits seem to accompany defects in code and can cause code to be difficult to change without introducing new defects. The following five good habits, when applied to your PHP code, will help you avoid these pitfalls.

Here's the list:

• Use good naming.
• Take smaller bites.
• Document your code.
• Handle error conditions.
• Never, ever, copy and paste.