In programming, writing working code is not the only responsibility of the developers. They are responsible for writing quality code that is extendable for future enhancements, as well as making sure the code is easily understandable for other developers. This is where coding standards become an important aspect of development. Coding standards are a set of rules and conventions specific to a programming language, and all developers are expected to follow them to make the code consistent.
I assume that you are familiar with PHP coding standards and ready to develop WordPress with that experience. However, WordPress itself has a set of coding standards and some of these rules are slightly different to PHP standards. The coding standards are currently divided into four sections, called PHP, HTML, CSS, and JavaScript. As a developer, you need to be familiar with WordPress coding standards, especially when you are developing themes and plugins for the WordPress repository.
Let's take a look at some of the main PHP coding standards used in WordPress:
- Single quotes and double quotes: PHP processes single quotes quicker than double quotes since the parser doesn't have to detect and execute any variables. That's why it's better to use single quotes for strings that don't have any evaluations.
- Indentation: You should use tabs instead of spaces for indenting the code.
- Opening and closing brackets: You should always use opening and closing brackets even when it's not necessary for single line evaluations.
- Using spaces: WordPress recommends putting spaces after commas, and on both sides of logical, comparison, string, and assignment operators.
- Naming conventions: You should always use lowercase letters and underscores for naming variables, functions, actions, filters, and so on. The camelCase method is not recommended in WordPress coding standards.
- Dynamic hooks: Hooks are unique to WordPress and hence the guidelines suggest using interpolation by wrapping the variable in curly brackets, instead of using concatenation.
These are some of the common coding standards for WordPress, and you can find the complete set of standards, including CSS, JavaScript, and HTML, at https://codex.wordpress.org/WordPress_Coding_Standards. Those developers who are familiar with pure PHP coding will notice the slight changes in WordPress standards, such as using lots of spaces and not using camel case for functions. So, it's a challenge even for experienced developers to come out of your comfort zone and write code the WordPress way.
The preceding section illustrated the main PHP coding standards. Most of you should have a general idea of these standards, as you have already worked with PHP. However, there are WordPress-specific coding styles/conventions due to hook-based architecture. Many of you may not be aware of these conventions, which are essential for building themes and plugins that don't conflict with others.
Let's have a quick overview of some of these conventions, which will be discussed in detail throughout the book:
- Loading scripts and styles: Usually, we can load scripts and styles anywhere in an HTML page by using <script> and <link> tags. WordPress uses built-in PHP functions to load scripts and styles. Therefore, it's recommended that you load these files only within an action called wp_enqueue_scripts. Loading these files outside this action could result in conflicts with WordPress core features as well as other plugins or themes.
- Loading third-party libraries: Libraries such as jQuery, Underscore, and Backbone.js are used frequently in modern web development. Usually, developers have the option to include these libraries within their code files or load them from a CDN for faster performance. This technique is not feasible in WordPress as many plugins from different developers are involved. Therefore, we need to load one common version of the library to avoid conflicts in code. So, we have to use the library version that comes built-in with WordPress.
- Using proper events for execution: In pure PHP programming, we can execute code anywhere and anytime based on our preferences. WordPress uses an event-driven architecture with hooks, and hence code is executed through events in a predefined manner. Unless we use the correct events, our code is going to conflict with code from other. For example, we need to access $_POST variables within or after an init hook. Trying to access this data before the necessary event could lead to errors in your code.
We had a brief introduction to the coding standards and conventions needed to get started with WordPress development. Often, you will find it sufficient for development projects for specific clients. However, you will sometimes need further knowledge, especially on event-based conventions for plugin and theme development. We will cover the necessary coding conventions throughout the upcoming chapters.
