how to create child WordPress plugin

I like to create child plugin..

Explanation :-

I have one parent plugin named X. This will work independently (like other existing plugins).

Now I decided to add some extra features to that plugin X (think of it as an upgrade). So I want to create extra features by way of another plugin Y, which will depend on (and inherit from) X.
This plugin Y will not work with out plugin X.

How can I do this?

Answers:

Thank you for visiting the Q&A section on Magenaut. Please note that all the answers may not help you solve the issue immediately. So please treat them as advisements. If you found the post helpful (or not), leave a comment & I’ll get back to you as soon as possible.

Method 1

the Best way to do this is have your X plugin made with its own hooks for actions and filters so new plugins (in your case Y) could interact with plugin X’s functions and data.
Defining your own hooks is fairly easy and simple.

Action Hook

from the codex:

Actions are the hooks that the
WordPress core launches at specific
points during execution, or when
specific events occur. Your plugin can
specify that one or more of its PHP
functions are executed at these
points, using the Action API.

example of a new action hook:

Function whatever(){
   //regular stuff you do normally 
  do_action('Name-Of-Your-Action-hook', $args1,$args2)
  //regular stuff you do normally
}

Now we can interact with that function and use its arguments ($args1,$args2) using ‘Name-Of-Your_hook’ hook

add_action('Name-Of-Your-Action-hook','hook_function_callback');

Filter Hook

from the codex:

Filters are the hooks that WordPress
launches to modify text of various
types before adding it to the database
or sending it to the browser screen.
Your plugin can specify that one or
more of its PHP functions is executed
to modify specific types of text at
these times, using the Filter API.

example of a new filter hook:

Function whatever(){
   //regular stuff you do normally 
   $output = apply_filters('Name-Of-Your-Filter-hook', $output,$args1,$args2)
  //regular stuff you do normally
}

Now we can interact with that function , filter $output use and its arguments ($args1,$args2) using ‘Name-Of-Your-Filter-hook’ hook

add_filter('Name-Of-Your_hook','hook_function_callback');

A good example to that would be contact form 7

• Contact Form 7 – Campaign Monitor
  Addon
• Contact Form 7 Dynamic Text Extension
• Contact Form 7 Calendar
• Contact Form 7 Textarea Wordcount
• Contact Form 7 Customfield in mail
• Contact Form 7 to Database Extension

and many more which all (most) are plugins that extend the functionality of Contact Form 7 based on its hooks.

Method 2

Make some hooks in your parent plugin to which the child plugin can attach their own function. Also wrap the child plugin in if(function_exists('parent-plugin-function')) or class_exists if its a class.

Method 3

I just went through myself and I had so many changes that I couldn’t just override the actions.

I created this tool that allows you to create a child plugin like a child theme. You can make updates to the plugin and still update it without losing your changes.

I’m posting this here because it relates and hopefully becomes useful to the next person who runs into this issue.

https://github.com/ThomasDepole/wordpress-child-plugin-tool

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0