What are the potential pitfalls of using popular CMS platforms like WordPress and Joomla for those looking to write their own modules and customize the code?

Potential pitfalls of using popular CMS platforms like WordPress and Joomla for writing custom modules and code customization include limited flexibility due to the platform's architecture, potential conflicts with existing plugins or themes, and difficulty in maintaining code updates across platform updates. To mitigate these issues, developers can opt for more lightweight CMS options or build custom solutions from scratch.

// Example PHP code snippet for creating a custom module in WordPress
function custom_module_function() {
    // Custom code logic here
}

add_action('init', 'custom_module_function');