WordPress plugin development

Must-use plugins (mu-plugins) in WordPress Besides normal plugins there is a second folder WordPress loads code from: wp-content/mu-plugins/. Files in it are “must-use” plugins: they are loaded on every request, before the normal plugins and the theme, and cannot be activated or deactivated in the admin.

Intuitive Custom Post Order plugin sorts posts wrong on the front end The Intuitive Custom Post Order plugin is a convenient way to sort posts by drag and drop in the dashboard. It saves the order in the menu_order field and adds that sorting to queries. But sometimes the order in the dashboard is one…

Upload files from a custom form to the WordPress media library Sometimes files come from a form on the site rather than from the admin: a photo for a listing, a CV for a job application, an avatar. WordPress has the functions to check such a file, move it to the uploads folder and create…

How to translate a WordPress theme or plugin WordPress has a built-in localisation system based on GNU gettext. The workflow: wrap translatable strings in translation functions, generate a .pot template, create a .po file for each language, compile it to a binary .mo file, and load the text domain in your theme or plugin.

How to enqueue a script after all other scripts in WordPress By default, WordPress prints scripts in the order they are enqueued, taking dependencies into account. Sometimes a script must run last, after jQuery and everything that other plugins have added to the page. The dependency list, a late hook priority and the wp_footer hook…

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.

Create your first custom block for the WordPress block editor Since WordPress 5.0 the editor is built from blocks, and a plugin or theme can add its own. A block is registered in JavaScript with registerBlockType(): the edit function describes how it looks and works in the editor, the save function returns the HTML that…

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…

Make a WordPress theme or plugin translation-ready A theme or plugin is translation-ready when every text the user sees goes through one of the WordPress i18n functions with the theme’s or plugin’s text domain. Then a translator only creates .po/.mo files, and nobody has to touch the code.