I wrote and maintain the theme for my wife’s website.

I installed everything I used on my laptop with these commands:

brew install composer php php-code-sniffer php-cs-fixer phplint phpmd phpstan \
    phpunit
pecl install xdebug

Testing Link to heading

For testing I’m using PHPUnit with CodeCoverage enabled (code coverage also requires Xdebug); I’ve been able to achieve near 100% test coverage (excluding functions.php which is now mostly configuration rather than code), and along the way I’ve improved and cleaned up the code significantly. The other PHP files in the theme are used automatically by Wordpress to display content of different types and have very little logic in them, so I don’t feel they are worth testing and testing would require faking lots of Wordpress functions.

I created a phpunit.xml config file using phpunit --generate-configuration plus editing so that I don’t have to keep supplying command line flags. Note that PHPUnit 9 and 10 have incompatible config files: although PHPUnit 10 will accept a config from PHPUnit 9, it will exit unsuccessfully, making it impossible to use in a pre-commit, so I have checked in both configs and symlink the correct one in each checkout.

I wrote some test helpers and fakes (e.g. FakeWordpress.php); I put them in src/ rather than test/ so code coverage would be measured for them - this gives me an easy way to spot unused code in test helpers that I can delete.

Linting Link to heading

Beware: there are many different style guides for PHP that seldom agree, so different tools might disagree over how your code should be formatted.

PHPLint Link to heading

I tried PHPLint because I’m a big fan of linters and style guides. I found it very, very restrictive - there is no way to suppress a warning, and its custom type annotations are intrusive. The biggest benefit I got from it is that I defined proper classes for holding data; for years I had followed the Wordpress approach of stuffing everything into an array, but the many complaints from PHPLint convinced me to define properly structured classes instead. Sadly I got there the long way and made lots of intermediate changes :( Several problems still stand out with PHPLint:

  1. There is no way to suppress warnings, see https://www.icosaedro.it/phplint/FAQ.html#H14_Can_I_turn_off_some_boring_error_PHPLint_signals?

  2. You need to add metadata to every file declaring which libraries are used by that file. I understand that for external libraries or optional libraries, but it’s silly to have to write /*. require_module 'core'; .*/ to tell PHPLint that core PHP functions will be used in this file. You can include a bigger set of modules, but then PHPLint will complain that you included unnecessary modules.

  3. PHPLint doesn’t support multiple module directory paths, so you either need to copy definitions for external libraries into the system path, or copy/symlink necessary files from the system path into a local directory and use --modules-path with the local directory; I chose option 2, and I wrote a wrapper program and a Makefile to make usage easier.

  4. The module declaration files use a slightly modified version of PHP function declarations, so I needed to generate some of the module definitions (see the wrapper program).

  5. PHPLint interprets cast(type, variable) to cast a variable to a different type. I didn’t want to include the PHPLint libraries so I wrote a fake version. This did not work when I added type annotations everywhere, because it works on many different types, so I deleted it because by that point I was using PHPStan (see below) rather than PHPLint.

  6. PHPLint has been broken far more often than it has been working, though it’s definitely possible that this is a problem with Homebrew packaging rather than PHPLint.

Overall I think PHPLint is too difficult and intrusive to be worthwhile, though I might feel differently if I had jumped directly to defining my own data structures. I got maybe 20% of the benefit I needed to justify the effort I put into it.

Other checkers Link to heading

I used PHPStan, and it mostly identified missing type annotations, which were easy to fix so it was a quick return on investment. I fairly easily reached level 8, but level 9 looked like a lot more work so I haven’t tried to reach that yet. I would recommend PHPStan over all the other linting and checking tools I’ve used for PHP. I needed to use Composer to add PHPUnit as a dependency for PHPStan to resolve the PHPUnit imports in my tests; composer require --dev phpunit/phpunit ^9 was all it took.

I used PHP Coding Standards Fixer to automatically fix some things that a linter would complain about. When I enabled the large sets of rules like @PhpCsFixer I was unhappy with the output, e.g. multi-line arrays and function calls had their indentation removed, which I strongly dislike. I read through the docs and picked out the rules I agreed with, put them in a .php_cs.dist config file, and enabled them one at a time to make small related changes I could easily review rather than one giant commit. Having tests made me confident that the tool hadn’t broken my code with the changes - yay for the tests! I had initially thought about testing out more of the rules in future, but an evening’s work has already gotten me good benefits, and further work looks like it will have very diminishing returns, so I’m happy with the investment of time I’ve made and probably won’t be investing any more.

I tried PHP_CodeSniffer but it produced a huge number of warnings and the documentation about configuring it is hard to follow, so I quickly gave up on that.

I tried PHP Mess Detector but PHP itself output ~1000 lines of deprecation warnings for the PHP Mess Detector code so I quickly gave up on that too. I tried it again later and it complained about boolean parameters and else branches on if statements, so I quickly gave up on it again.

Breaking up functions.php Link to heading

functions.php is the Wordpress theme file that most documentation will tell you to modify, and for several years I put every new function into it, leading to a mixed up mess of code. Breaking up functions.php into separate files while writing tests has had multiple benefits:

  • It’s much easier to understand a piece of functionality because all the related code is in an individual file rather than jumbled up with lots of other code.
  • Writing tests was much more satisfactory because I had intermediate targets to hit 100% coverage on rather than a single gigantic file where progress would be glacially slow. I wouldn’t ever get to 100% coverage on functions.php anyway because too much of it is Wordpress configuration that can’t be meaningfully tested in isolation.
  • I improved the code as I wrote the tests by removing unnecessary code, making cleaner interfaces, and breaking spaghetti code down into separate functions. This was all easier when working on small piece of functionality than it would have been working on everything at once. The code grew in size by approximately 200 lines or a factor of 1.158.

functions.php still exists, but it’s now 148 lines long rather than 1226 lines long!