Tips for How to write Better Code

Use a Coding Standard
It’s easy to write a line of code, unorganized code, but it’s hard to maintain such code. Good code typically follows some standard for naming conventions, formatting, etc. Such standards are nice because they make things deterministic to those who read your code afterwards, including yourself.You can create your own coding standard, but it’s better to stick to one with wider-acceptance.

Write Useful Comments
Comments are crucial. You won’t appreciate them until you leave your thousand-line script for a couple of days and return to and try and make sense of it. Useful comments make life easier for yourself and those after you who have to maintain your code.
Write meaningful, single line comments, write full parameter and functionality descriptions for functions and methods, for tricky logic blocks, describe the logic in words before it if necessary. And don’t forget, always keep your comments up to date!

Code refactoring
Code refactoring is a good habit of highly effective developers. Believe it or not, you should be refactoring your code on a daily bases or your code is not in good health! Refactoring keeps your code healthy, but what should you refactor and how?
You should be refactoring everything, from your architecture to your methods and functions, variables names, the number of arguments a method receives, etc.
How to refactor is more of an art more than a science, but there are a few rules of thumb that can shed some light on it:
aIf your function or method is more than 20-25 lines, it’s more likely that you are including too much logic inside it, and you can probably split it into two or more smaller functions/methods.b-If your method/function name is more than 20 characters, you should either rethink the name, or rethink the whole function/method by reviewing the first rule.c-If you have a lot of nested loops then you may be doing some resource-intensive processing without realizing it. In general, you should rethink the logic if you are nesting more than 2 loops. Three nested loops is just horrible!Consider if there are any applicable design patterns your code can follow. You shouldn’t use patterns just for the sake of using patterns, but patterns offer tried-and-true ready-thought solutions that could be applicable.

Avoid Global variables
Global variables and loops are a mess and can prove problematic when your application grows to millions of lines of code (which most do!). They may influence code elsewhere that is difficult to discern, or cause noisy naming clashes. Think twice before you pollute the global namespace with variables, functions, loops, etc.
In an ideal case, you should have no blocks defined globally. That is. all switch statements, try-catch, foreach, while-loops, etc. should be written inside a method or a function. Methods should be written inside class definitions, and class and function definitions should be within namespaces.

Always Use Meaningful Names
Never use names like $xyz, $abc, and $test1 for your variables. How do expect to read such code in the future? Good code should be meaningful in terms of variable names, function/method names, and class names. Some good examples of meaningful names are: $request, $dbResult, and $tempFile (depending on your coding style guidelines these may use underscores, camelCase, or PascalCase).

Always Use Meaningful Structures
Structuring your application is very important; don’t use complicated structures, always stick to simplicity. When naming directories and files, use a naming convention you agree upon with your team, or use one associated with your coding standard. Always split the four parts of any typical PHP application apart from each other – CSS, HTML Templates/Layouts, JavaScript, PHP Code – and for each try to split libraries from business logic. It’s also a good idea to keep your directory hierarchy as shallow as possible so it’s easier to navigate and find the code you’re looking for.

Use Version Control Software
In the old days, good development teams relied on CVS and diff patches for version control. Nowadays, though, we have a variety of solutions available. Managing changes and revisions should be easy but effective, so pick whatever version control software that will work best with the workflow of your development team. I prefer using a distributed version control tool like Git or Mercurial; both are free software/open source and very powerful.

Use Code Documenters
For large applications spanning several classes and namespaces, you should have automatically generated API documentation. This is very useful and keeps the development team aware of “what’s what.” And if you work on several projects at the same time, you will find such documentation a blessing since you may forget about structures switching back and forth between projects. One such documenter you might consider using is DocBlox.

Use a Testing Framework
There are a plenty of tools that I really appreciate, but by far the ones I appreciate the most are the frameworks that help automate the testing process. Testing (particularly systematic testing) is crucial to every piece of your million dollar application. Good testing tools are PHPUnit and SimpleTest for unit testing your PHP Classes. For GUI testing, I recommend SeleniumHQ tools.