Building a website quickly with WordPress is highly popular, but many developers rush and make poor choices. Simple errors, like leaving WP_DEBUG on, are easy to make. Others, like combining all JavaScript into one file, are common among less diligent developers. Whatever your misstep, this article outlines the 12 most frequent WordPress blunders by both new and experienced developers. If you’re making any of these mistakes, don’t worry, they’re learning opportunities.

1. Merging WordPress Theme JavaScript into One File

During website optimization, I found a client using a premium theme with all JavaScript, including custom code, in a single file like main.js, theme.js, or custom.js. This is detrimental for several reasons:

1. The file can become massive as the theme expands, reaching even 1 MB. Loading this site-wide, even when only a fraction is needed, slows down page downloads and rendering, especially with render blocking code in the head section.
2. Managing the code becomes difficult. Using functions like wp_dequeue_script() to selectively unload code for speed or to avoid conflicts becomes impossible. While splitting and enqueuing is possible, theme updates to main.js require repeating the process.

2. Using Generic Names for Variables, Functions, Constants, or Classes

When building a plugin, a unique naming convention avoids conflicts with other plugins. Many developers use prefixes related to the plugin for easy identification. Others prefer PHP namespaces to encapsulate elements and address two issues:

1. Name clashes with internal PHP, third-party code, or constants.
2. The ability to shorten long names for readability. This is my favorite for code-heavy themes and plugins, allowing for easy management without worrying about long, unique names.

Understanding namespaces is crucial to avoid misuse.

Project requirements might dictate adhering to existing coding styles, especially when extending existing codebases. For consistency, follow the established PHP coding standards for WordPress. Universally applied performance optimizations, like using single quotes for non-evaluated strings and proper code indentation, should be maintained regardless of the style guide.

3. Underutilizing WordPress Core Functionality

WordPress offers a range of updated libraries for plugins and themes. I’ve seen themes and plugins include files like jQuery or Color Picker, already present in WordPress core. This increases package size, loading times, and update management overhead.

Utilize existing WordPress features. The core team keeps libraries updated, resulting in a lighter and maintainable project. Regular WordPress updates provide access to new features and improve security by patching vulnerabilities.

4. Making Plugins or Themes Difficult to Modify without Direct Editing

Directly editing WordPress plugins or themes is ill-advised unless you’re a contributor. Updates will overwrite changes, requiring repeated edits.

Using actions, filters, and Child themes is more effective. These approaches modify functionality without touching the parent code. When offering a free plugin with potential premium extensions, design it for easy expansion.

5. Developing with WP_DEBUG Disabled

By default, WP_DEBUG is off, suppressing PHP errors for security reasons on live sites. During development, enabling it is crucial for catching errors. Addressing these errors, even minor ones, enforces good coding practices and ensures your code is error-free across WordPress installations.

Experienced developers understand this, but it’s sometimes overlooked in haste. Prioritize WordPress coding standards and PHP best practices, no matter the urgency.

6. Writing PHP Code Without Considering Caching

This common PHP error, avoidable by following coding standards, occurs when developers write code dependent on constant execution. For example, a function reacting to the User Agent for actions like enqueuing mobile-specific scripts.

Caching plugins can render such code useless if conditions aren’t triggered. Responsive design should be handled through front-end solutions like media queries and JavaScript (only when absolutely necessary).

7. Not Using Version Control (Like Git)

Custom-coded files, like child themes or plugins, should be under version control. Git tracks changes, enabling collaboration and easy reverts to previous versions. For clients, Git provides a history of work done on their project, especially for large, long-term custom websites.

Git might seem intimidating initially, but understanding it is invaluable. GUIs like SourceTree simplify interaction and learning. Once comfortable, explore advanced Git best practices for further optimization.

8. Unnecessary Enqueuing of CSS and JavaScript Files

Numerous HTTP requests slow down websites, impacting Google PageSpeed scores and potentially SEO rankings. It can also cause conflicts. For instance, multiple plugins loading the same jQuery library can lead to issues.

9. Using .php Files for CSS or JavaScript Output

Some themes and plugins use files like style.php to generate CSS based on database-stored settings. This is detrimental to performance:

1. Loading CSS within the head tag delays rendering until the file is fully downloaded, especially problematic on slow WordPress environments. Even with caching, using a static .css file is more efficient.
2. Mixing CSS rules with PHP variables and conditionals in the .php file hinders readability for developers trying to debug or understand the code.

The solution is to save custom CSS outside the plugin directory, like in /wp-content/uploads/theme-name-custom-css/style-5.css. This preserves the file during theme or plugin updates.

10. Neglecting Proper Architecture for WordPress Plugins and Themes

Choosing the right architecture depends on the plugin’s size and purpose. For small, single-purpose plugins, complex classes are unnecessary unless significant expansion is anticipated.

For feature-rich plugins with extensive code, an OOP approach with classes is beneficial. For example, separate classes for shortcodes or script handling improve organization.

Implementing the MVC pattern keeps HTML and PHP separate, enhancing maintainability. Avoid embedding HTML within PHP methods, especially for collaboratively maintained plugins.

The WordPress Plugin Handbook suggests three broad architecture patterns:

• Single plugin file, containing functions
• Single plugin file, containing a class, instantiated object, and, optionally, functions
• Main plugin file, then one or more class files

11. Overlooking WordPress Security

Security is often neglected in favor of client demands. However, neglecting it can have severe consequences, leading to website hacks and plugin vulnerabilities. Even the WordPress core has had its share of security issues. We must prioritize security and respond swiftly with well-tested patches if vulnerabilities arise.

Essential security tips:

XSS Vulnerabilities: Sanitize both input and output data. WordPress offers various methods for this depending on the context. Never trust input or data before printing it. For input, functions like sanitize_text_field() are crucial. For output, use functions like esc_url() to securely display links.

Prevent Direct File Access: Hosts often allow this, and improper code can expose sensitive information through errors. Using code snippets like:

1
2

// Exit if accessed directly
if ( ! defined( 'ABSPATH' ) ) exit;

prevents unauthorized access.

Use Nonces: As defined in the WordPress documentation, nonces protect URLs and forms from misuse.

For example, the URL http://example.com/wp-admin/post.php?post=123&action=trash—When` deletes a post after authentication.

Attackers can exploit this by creating malicious links like <img src="__TOKEN_12__" /> that hijack authentication cookies.

Nonces mitigate this by adding a unique value: http://example.com/wp-admin/post.php?post=123&action=trash&_wpnonce=b192fc4204 making exploitation significantly harder.

While many rely on hosting providers and commercial plugins for security, conducting regular penetration tests is crucial for identifying and fixing vulnerabilities before attackers exploit them.

Remember, many attacks are automated. Bots scan for known vulnerabilities and exploit them for spamming, data theft, or injecting malicious links. Some hacks are subtle, requiring thorough website scans to detect. Reinstalling WordPress, even with the same version, can overwrite compromised files.

12. Using WordPress Functions and Code Without Understanding

Developers often copy-paste solutions from sources like StackOverflow without understanding the logic or potential for optimization.

This can lead to:

1. Inconsistent coding styles, especially problematic for commercial projects requiring uniformity.
2. Inefficient code due to the use of suboptimal functions, leading to performance issues and maintainability problems.
3. Potential licensing conflicts when using code snippets without proper attribution, opening up clients to legal risks.

Continuous Learning

Everyone makes mistakes; they are opportunities for growth. The fast-paced nature of WordPress development means there’s no single “right way” to do things. Continuous learning and practice are key to improvement.

Do you have different views on these mistakes or any to add? Share your thoughts in the comments for discussion!