PHP for WordPress developers

PHP 8.1 enums, readonly properties and intersection types in a WordPress plugin PHP 8.1 brought three features that make plugin code stricter with little effort. Enums replace groups of string constants, so an invalid status is a type error instead of a silent bug. Readonly properties make value objects that cannot change after construction. Intersection…

Write unit tests for WordPress plugins with PHPUnit and WP-CLI scaffolding WordPress unit tests run against a real WordPress loaded with a separate test database. Every test runs inside a database transaction that is rolled back afterwards, so each test starts from a clean state. WP-CLI generates the whole setup, and the base class WP_UnitTestCase…

Closures and arrow functions in WordPress hooks Anonymous functions are a convenient way to write a short hook callback right where it is added. PHP has had closures since 5.3 and arrow functions (fn() =>) since 7.4. In WordPress they come with two things to know: how variables from the surrounding code get into them,…

PHP 8.0 for WordPress developers: match, named arguments, nullsafe and more PHP 8.0 was released on November 26, 2020. It brings the biggest set of language changes since PHP 7.0: the match expression, named arguments, the nullsafe operator, union types, constructor property promotion, and a JIT compiler. WordPress 5.6, due on December 8, ships with…

Composer in WordPress plugins and themes Composer is the dependency manager of PHP. WordPress core does not use it, but in your own plugins and themes it saves copying libraries by hand: composer require downloads a library with its dependencies, and one autoloader loads all classes, the libraries’ and your own.

Debug WordPress with Xdebug and VS Code var_dump() and error_log() show one value at one moment. A step debugger stops the code on a line you choose and shows all variables, the call stack and the current hook, and lets you go on line by line. For WordPress, with its chains of hooks and filters,…

PHP 7 features worth using in WordPress code PHP 7.0 came out in December 2015 and was roughly twice as fast as PHP 5.6 on WordPress, but it also brought language features that make code shorter and clearer. WordPress itself still runs on PHP 5.2.4 and newer, so core cannot use them, but in your…