What are common pitfalls when using PHP to modify plugins in Wordpress?

One common pitfall when modifying plugins in WordPress using PHP is not properly checking for the existence of functions or hooks before modifying them, which can lead to fatal errors or conflicts with other plugins. To avoid this, always use conditional statements to check if a function or hook exists before modifying it.

if (function_exists('some_function')) {
    // Modify the function here
}