Overriding functions in wordpress plugins

Question

I notice that in some plugins you can override functions by ...

1. Creating an uploads folder
2. Creating a folder with the plugin name

3. Using the following code

   if (!function_exists('function_name')) {
       function function_name() {
   
       }
   }
   

Is this standard for all Wordpress plugins or only if they're written in a specific way?

Answer 1

If the plugin displays content via any function, the code:

if(!function_exists('function_name')) function_name();

... is used for safety.

If your plugin is disabled, and the if (!function_exists('function_name')) is missing, your theme will throw a fatal error.

Answer 2

These are referred to as pluggable functions, and are intended to be able to be over-ridden, either by Plugins, Themes, or Child Themes.

It is only standard for functions that are intended to be over-ridden - and, generally speaking, the better practice is to add filter hooks to function outputs, rather than making functions pluggable.