Developing a Custom WordPress Plugin: Considerations, Insights & Best Practices

WordPress is a powerful tool. There’s a lot it can do with very little setup required, excelling at creating easy-to-manage websites that are functional and responsive. WordPress is also open source, with a thriving community of developers that have contributed to creating a vast marketplace of themes and plugins covering a variety of requirements that aren’t handled by default. 

While 3rd party plugins from the marketplace can tackle common problems and further extend this functionality, what if you need something completely unique? Maybe you want a custom booking system that integrates seamlessly with your brand, a dashboard that tracks real time updates in an API, or an extension that displays up-to-date information on sports events as they happen. This is where custom plugins come in. The points we’ll cover include:

WordPress Theme vs Plugins

Before we get into why you might want to use a plugin, you might be asking: ‘what’s the difference between updating my theme and creating a custom plugin?’

Theme

A WordPress theme is used to represent the design of your website. It’s a collection of different code files that make up the layout of your site, such as PHP templates and CSS stylesheets, possibly with JavaScript for interactivity. Themes control design appearances such as layout, colours or typography.

Plugin

Plugins are used on WordPress websites to include and extend functionality beyond what’s available in your theme. They don’t change layouts, but rather expand the capabilities of the existing theme. A plugin does not depend on a theme, and could be installed on many different themes.

Limitations of 3rd Party Plugins

Plugins from the marketplace come in many different shapes and sizes, with many tens of thousands of plugins available right now. If it’s a common operation on the web, chances are there’s a plugin for it. Think solutions for SEO, security, form building, analytics, social media, custom block plugins, API integrations, and much more. 

So, what if it’s not a common problem? Maybe you need something highly specific, or something that fits perfectly with your brand like no 3rd party plugin can quite recreate. Maybe you’re just hesitant about leaving a critical aspect of your site in the hands of unknown plugin authors that could stop releasing updates. Whatever it may be, if an off-the-shelf solution isn’t quite ticking all the boxes, it’s probably time to start looking at the custom route.

Why Use a Custom WordPress Plugin?

Bespoke Functionality

As we’ve briefly touched on, a custom WordPress plugin can be a fantastic solution to a unique problem. This is because it removes many of the barriers that are put in place by the CMS or by using other plugins that are created to be a ‘one size fits all’ solution. There’s a good chance you’re going to need to accept some level of compromise when choosing an existing plugin from the marketplace, and sometimes compromise is not an option. A tailored approach means you solve the exact problem you’re facing.

Reduce Bloat and Improve Site Performance

Plugin bloat is one of the biggest culprits of poor site performance in WordPress systems. This circles back to a lack of specificity in order to entice as many potential users as possible, but this leads to having suites of unused features present on your website, negatively affecting speed.

In other cases, a single plugin may not achieve everything you need, leading to you installing multiple plugins to accomplish your goal. These workarounds are often harmful to the efficiency of your site.

Creating your own plugin allows you to be precise with your requirements, ensuring you get exactly what you need without the bloat.

Improve Security and Maintainability

Using a 3rd party plugin means you need to rely on the developers to keep it both secure and up-to-date with your version of WordPress. A plugin could become unsupported at any time, and there’s no guarantee that one of your vital extensions will be maintained for as long as your website needs it. 

Your site security can also be compromised should a plugin fail to address issues or stop releasing updates. When this happens, you’re at the mercy of the original developers to get the issue resolved in a timely manner, or at all. If the features were required for your website to function, users may not be able to use it.

Integrate with 3rd Party Services

A major challenge many website owners face is finding tools that seamlessly integrate with their external platforms. This could be anything from a custom API, a CRM, or analytics platform. Finding a tool that unifies these processes in one place in an efficient manner is harder than you might think, and potentially impossible without paying subscriptions for premium plugins if you have a bespoke system.

Taking development into your own hands opens up a world of possibilities and customisation that could not be possible otherwise.

Considerations for Creating a WordPress Plugin

We’ve developed and deployed numerous custom plugins successfully for our clients, and we’ve picked up a few tricks on the way, learning some valuable lessons at the same time. We’re not ones for secrets, so let’s take a look at some things, technical and non-technical, that you should consider when creating a plugin of your own.

Technical Considerations

Understand the Website You’re Building For

One of the first things we look at when starting a plugin is how the existing website is set up. This is crucial to ensure the plugin we’re building will be compatible when installed and will run as expected. We ensure we have a solid understanding of the PHP, WordPress and SQL versions running on the site before we get to work. This allows us to write code in a way that is appropriate for the active software on the website.

Performance Impact

We discussed how custom plugins can speed up your website by reducing bloat, but this isn’t something that happens automatically without careful consideration for how your plugin should achieve its goals.

A lot goes into this, and it’s a large part of the work that goes into development. For example, on a recent project, we created a plugin that periodically polled a 3rd party API, processed this data and inputted it into a custom database, where the plugin could later request it when users visit parts of the site. This required a strong working knowledge of WordPress’s internal scheduling system and creating performant operations to request data from the API. These kinds of optimisations are some of the most important things to consider when creating your own plugin.

How to Measure Performance

Understanding the impact of each piece of a plugin can be tricky, which is why we recommend getting a helping hand from a reputable performance metric tool. These tools give you precise, empirical guidance on the real world performance of the feature you’re testing.

Query Monitor

Query Monitor is a free plugin that is advertised as the ‘developer tools for WordPress’. It offers a suite of debugging tools for database queries, PHP errors, scripts/stylesheets, custom blocks, API calls, and more. It’s particularly handy for this case as you can view reports grouped by plugin, meaning you can diagnose issues directly related to your code. If your page is visibly slow, we recommend first looking at the database queries made by your plugin. This will help you optimise your database requests with speed in mind.

Lighthouse / PageSpeed Insights

Both of these developer tools from Google are helpful for overall health checks and can quickly give you an idea of how a page is performing. The categories that are measured are performance, accessibility, best practices and SEO. While these give you a great overview of the health of a webpage, it’s difficult to isolate the impact of your plugin.

GTMetrix

GTMetrix offers similar analysis to PageSpeed Insights but also provides deeper insight into the performance metrics and offers a waterfall chart that allows you to debug the page load pipeline, clearly pinpointing where load times are suffering. This can help you visualise long-running script evaluation, excessive HTTP requests, or any other blocking time easily.

User Experience

From a frontend perspective, a user shouldn’t be able to tell a plugin is an add-on of your site, but should view it as a part of your site as a whole. Well thought out UX principles are vital in maintaining your brand between your main site and the features the plugin offers. Collaboration with design specialists close to the brand is an important part of our process that reduces friction between proposed ideas and existing content.

We also recommend thinking about how a backend user might be likely to use your plugin, and what settings they might need to adjust in WordPress. Our approach is to imagine ourselves in the shoes of our client, which helps us think about common processes they may want to achieve when using our plugin. This aids us in creating an intuitive admin page where users can easily adjust whatever they may need to.

Error Handling

As is the case with making anything complex, problems arise during development and testing, and occasionally even in production. As developers, we need to ensure that errors are handled elegantly. This means handling code errors in a fashion that clearly logs the issue, if/where appropriate, to aid with troubleshooting, while avoiding exposing sensitive information at the same time.

Software Versioning

Software versioning is the process of assigning unique version names or numbers to a software release in order to differentiate it from past and previous versions. Versioning is cemented into our development process for any plugin we create. This makes the handover of plugin files simple and also allows us to easily pinpoint issues in between versions. 

Non-Technical Considerations

Scalability

How is your plugin going to be used? How might it grow in the future? How can it be extended with additional features? While these questions verge on the technical, we see this as an important early question before building starts and as it continues. Making sure work carried out in early stages doesn’t have to be completely rewritten when specifications slightly change or a userbase grows can be a huge timesaver.

Branding

Make the most of your design freedom by channelling your brand as you wish it to be seen in your plugin. At the basic level, keep it consistent with the rest of the website with a matching logo, theme, name and description.

Legal Regulations/Data Privacy

If you’re thinking about handling user data, using cookies, or promoting anything requiring terms and conditions, you need to follow strict guidelines to avoid being penalised. These guidelines vary depending on what you’re looking for. In our experience, auditing these requirements at an early stage allows you to be prepared to handle them, whether it be utilising a Consent Mode V2 compliant cookie solution, or adhering to GDPR best practices.

Time Investment

As you might expect, there’s a tradeoff to consider in time and effort spent on getting your plugin set up. Undeniably, 3rd party plugins have a quick setup time (at the cost of flexibility and support), whereas a custom solution needs to be developed from scratch. While the freedom you get with a custom plugin is unparalleled, there’s no doubt that you need strong technical expertise to manage development and deployment to achieve that end result.

Best Practices for Creating a WordPress Plugin

Since you’re creating a plugin for WordPress, it must conform to technical best practices to guarantee that it integrates with WordPress Core and any other WordPress plugins. It’s important to view your plugin as an extension of the site you’re building for, and not something that runs in an isolated environment. Best practices aren’t simply a list of technical considerations; you also must consider the client and the end user from a practical standpoint.

Folder Structure

Logical file organisation is an often overlooked portion of plugin development. Having a sensible folder structure in your plugin repository means you and others working on the project can easily navigate the code and make reasonable assumptions on where new pieces of code should go. A sample folder structure as outlined by WordPress:

/plugin-name
     plugin-name.php
     uninstall.php
     /languages
     /includes
     /admin
          /js
          /css
          /images
     /public
          /js
          /css
          /images

Avoid Plugin Conflicts

Plugin conflicts such as naming collisions can have site-breaking effects. As you might imagine, it’s crucial to avoid such circumstances. There are a few different standards you should follow when writing plugin code:

Prefix Code

Prefixing all globally accessible function, class and variable names with a consistent and unique naming convention greatly reduces the chance of naming collisions. WordPress states that prefixes should be at least 4 characters long, though they recommend 5, and should avoid using common English words that could be used elsewhere.

Check for Existing Code Implementations

There are various different functions provided by PHP that allow you to verify the existence of functions or variables. These functions return true if the entity you’re checking for exists. These prevent errors by stopping you redeclaring statements. 

Boilerplate Starting Points

Plugins often come from a similar starting point. There are probably things you’ll do during the setup phase of every project, which is why you could save time by using boilerplate to get you started. WordPress even offers this boilerplate as a good starting point.

Quality Assurance

In our experience, testing a newly developed plugin is as important as any other phase of the project. Bugs present themselves in many different ways at various stages in the development process, which is why a rigid and thorough testing process is vital to delivering a reliable piece of software. The goal here is to ensure software quality while minimising defects. Tests should be carried out against a set of predetermined criteria, usually a functional specification, to ensure the end result meets the expectations of the original brief. The process should be carried out across a variety of devices and browsers to cover all bases, giving you the best chance at finding and squashing all those bugs.

Documentation

Well thought out documentation vastly increases the user experience of your plugin. It should help users quickly understand how to install, configure and use the plugin. Having documentation in place also helps reduce support requests by helping users troubleshoot issues on their own as well as having access to FAQs or support guides. Key areas to document for a WordPress plugin include:

Plugin Introduction/Installation

This is a chance to introduce the plugin, its purpose and its benefits. This could also include any requirements, such as the PHP version. Use this section to describe the steps for installation as well.

Setup

If there’s any setup required before the plugin can start working, you should dedicate a section to this process, guiding the user through the necessary steps.

Feature Documentation

Use this section to list in detail each key feature in your plugin, as well as any step-by-step instructions on performing important tasks. You might include any customisation options for these features.

Troubleshooting/FAQs

Provide users with a guide for troubleshooting commonly experienced problems and list any frequently asked questions. If relevant, a developer debugging guide could also be useful. As mentioned, this information could reduce the amount of support requests received in the future.

These are just a few of the key areas to consider listing in your documentation. Depending on the type of plugin you’re developing, and whether this is for the public or a private client, you may also include: support or contact information, security and best practices, a changelog, developer documentation, etc.

WordPress plugins are powerful tools that can allow you to deeply customise your website, but there’s plenty that goes into creating one. We understand that can be an overwhelming process, but one that can reap great benefits. That’s why we’re here to help. We have years of experience of developing custom features for WordPress. If you need a hand or have any questions surrounding custom WordPress plugin development, then get in touch and we’d be happy to have a chat with you.