How To Create A WordPress Plugin

WordPress Plugins allow users to easily modify, customize, and enhance any WordPress website. Instead of changing the core software WordPress is built on you can rather create a plugin to extend it. Using plugins allows you to have the most optimized WordPress installation all while maximizing how you use the software to begin with.
This article will walk you through the steps in creating a WordPress plugin.

What is a WordPress Plugin?

Here is the basic definition found on the WordPress Codex.

WordPress Plugin: A WordPress Plugin is a program, or a set of one or more functions, written in the PHP scripting language, that adds a specific set of features or services to the WordPress weblog, which can be seamlessly integrated with the weblog using access points and methods provided by the WordPress Plugin Application Program Interface (API).

Creating a Plugin

When creating a WordPress plugin there are some standards to uphold to when doing so. Below I’ll outline some key points to remember when creating your own.

Plugin Name

If you’re planning on making a plugin that doesn’t exist yet you will need to first determine its name. To be extra sure you will want to do a search in the WordPress Plugin repository. Some developers choose a name that describes more of what the plugin does so the end user can establish a quick connection with the name. The name itself can be multiple words.

Plugin Files

Typically a plugin lives within its own folder under wp-content/plugins/ inside your WordPress installation. There is usually at least one PHP file that is typically named after the plugin. So if your plugin was named amazing-plug then your PHP file name would most likely be amazing-plug.php. Using a unique name is crucial so no two plugins use the same name.
You can also choose to split your plugin into multiple files; similar to the way WordPress is built. Assets such as images, CSS, and JavaScript are common to see within installed plugins.

Readme File

Readme files are useful for other developers and users. Usually these files give a quick description of the plugin as well as sometimes offer change logs which indicate previous updates and maintenance announcements to users.

Home Page

If you plan to share you plugin with the WordPress community, having a dedicated home page would be wise. This page can be used as a place to download the plugin, report bugs, and announce updates to your user community.

Standard Plugin File

A plugin must contain a bit of meta information which tells WordPress what it is and how to handle it within your website. Plugins can be installed, deleted, activated, and inactivated. A standard header is introduced below to establish your plugin’s presence. The parameters shown will tell WordPress how to optimize it within your website and WordPress admin area.

<?php

/**

* Plugin Name: My Plugin Name

* Plugin URI: http://mypluginuri.com/

* Description: A brief description about your plugin.

* Version: 1.0 or whatever version of the plugin (pretty self explanatory)

* Author: Plugin Author's Name

* Author URI: Author's website

* License: A "Slug" license name e.g. GPL12

*/

The minimum WordPress needs to establish your file as a plugin is the line

Plugin Name: My Plugin Name

The rest of the information will be displayed within the Admin area under the Plugins section.

Programming the Plugin

Now the time comes to create our own demo plugin. I’ll be working on a local copy of WordPress using the our Divi 2.0 theme. You can follow along whichever method you prefer but to limit any downtime on your website I suggest you work locally or on a testing server. Our blog features other posts about installing WordPress locally if you are new to the concept. Find the links below depending on your platform.
Links:

• How To Install WordPress Locally On A Windows Computer
• How To Create A Local WordPress Installation On A Mac

For this tutorial I will be creating a plugin that creates a custom post type for our blog as well as establishes some other custom parameters. This plugin will be useful because we will be able to use it among any theme rather than just modifying one.

Plugin Scope

Our plugin will start with a simple PHP file. We will call this file custom-music-reviews.php. Within our file we will create a custom post type as well as define some new categories within that post type. The purpose of this plugin will be to write music reviews within specific genres without needing to touch code in the future. Each review will have a feature image, excerpt, rating, and genre type.

Starting Off

Assuming you have a local copy of WordPress ready to use, navigate to your wp-content folder inside of a code editor of your choice. Inside that folder you should see a folder called plugins. Inside of that folder create a new folder called custom-music-reviews.
With the folder created create a new file inside it called custom-music-reviews.php.
The path to the file should now be wp-content/plugins/custom-music-reviews/custom-music-reviews.php.
With your new file created we need to add some parameters in comment form like I explained earlier. For our plugin our parameters will look like this:

<?php

/**

* Plugin Name: Custom Music Reviews

* Plugin URI: http://elegantthemes.com/

* Description: A custom music review plugin built for example.

* Version: 1.0

* Author: Andy Leverenz

* Author URI: http://justalever.com/

**/

With this information added, save your file and navigate to your WordPress admin area. Click on Plugins on the left side navigation and you should now see our plugin available. Wasn’t that easy?

With our parameters in place our plugin becomes available to activate under “Installed Plugins”.

Even though our file is empty we can go ahead and activate the plugin. Go ahead and do that now. You’ll hopefully notice nothing different about your site with the plugin activate. If you do you probably typed the content above wrong or failed to close the comment.

Adding Our Plugin Code

With our file all set up and plugin active we can now add the inner workings of the plugin which we will be using for this tutorial.
Add the code below:

// Register the Custom Music Review Post Type

function register_cpt_music_review() {

$labels = array(

'name' => _x( 'Music Reviews', 'music_review' ),

'singular_name' => _x( 'Music Review', 'music_review' ),

'add_new' => _x( 'Add New', 'music_review' ),

'add_new_item' => _x( 'Add New Music Review', 'music_review' ),

'edit_item' => _x( 'Edit Music Review', 'music_review' ),

'new_item' => _x( 'New Music Review', 'music_review' ),

'view_item' => _x( 'View Music Review', 'music_review' ),

'search_items' => _x( 'Search Music Reviews', 'music_review' ),

'not_found' => _x( 'No music reviews found', 'music_review' ),

'not_found_in_trash' => _x( 'No music reviews found in Trash', 'music_review' ),

'parent_item_colon' => _x( 'Parent Music Review:', 'music_review' ),

'menu_name' => _x( 'Music Reviews', 'music_review' ),

);

$args = array(

'labels' => $labels,

'hierarchical' => true,

'description' => 'Music reviews filterable by genre',

'supports' => array( 'title', 'editor', 'author', 'thumbnail', 'trackbacks', 'custom-fields', 'comments', 'revisions', 'page-attributes' ),

'taxonomies' => array( 'genres' ),

'public' => true,

'show_ui' => true,

'show_in_menu' => true,

'menu_position' => 5,

'menu_icon' => 'dashicons-format-audio',

'show_in_nav_menus' => true,

'publicly_queryable' => true,

'exclude_from_search' => false,

'has_archive' => true,

'query_var' => true,

'can_export' => true,

'rewrite' => true,

'capability_type' => 'post'

);

register_post_type( 'music_review', $args );

}

add_action( 'init', 'register_cpt_music_review' );

This code above may look like a lot and almost seem like an unknown language to you if you’re new to WordPress but if not you’ll recognize this code as a Custom Post Type. In this case our custom post type is called music_review. The code is essentially telling WordPress to establish a new type of post within your theme. The post type has parameters that go along with it such as labels, arguments, and more. I won’t go into a ton of detail on how Custom Post Types work because I’ve already covered it within another article on Elegant Themes. Be sure to read it to gain a full understanding.
With our post type set up you can already see it active within the WordPress admin area.
Our custom post type is successfully implemented.
Lets take things one set further and include a custom Taxonomy called Genre inside our plugin. Think of a Taxonomy as a type of categorizing feature that is completely custom. WordPress already includes Categories and Tag support by default but developers can create custom taxonomies to extend their themes or plugins even further.
Read more about WordPress Taxonomies here.
Add the code below under the custom post type function we just added.

function genres_taxonomy() {

register_taxonomy(

'genres',

'music_review',

array(

'hierarchical' => true,

'label' => 'Genres',

'query_var' => true,

'rewrite' => array(

'slug' => 'genre',

'with_front' => false

)

)

);

}

add_action( 'init', 'genres_taxonomy');

Registering a new Taxonomy is relatively easy. We have made the connection to our custom post type by using the
register_taxonomy() function which creates a new taxonomy called genres and assigns it to our post type music_review.
We need to add one more line to our custom post type to make everything sync up. Add this code just below the supports argument within the custom post type.
Here’s all our plugin code up until this point. For better legibility I’ve stripped our code of any comments we had prior to this.

function register_cpt_music_review() {

$labels = array(

'name' => _x( 'Music Reviews', 'music_review' ),

'singular_name' => _x( 'Music Review', 'music_review' ),

'add_new' => _x( 'Add New', 'music_review' ),

'add_new_item' => _x( 'Add New Music Review', 'music_review' ),

'edit_item' => _x( 'Edit Music Review', 'music_review' ),

'new_item' => _x( 'New Music Review', 'music_review' ),

'view_item' => _x( 'View Music Review', 'music_review' ),

'search_items' => _x( 'Search Music Reviews', 'music_review' ),

'not_found' => _x( 'No music reviews found', 'music_review' ),

'not_found_in_trash' => _x( 'No music reviews found in Trash', 'music_review' ),

'parent_item_colon' => _x( 'Parent Music Review:', 'music_review' ),

'menu_name' => _x( 'Music Reviews', 'music_review' ),

);

$args = array(

'labels' => $labels,

'hierarchical' => true,

'description' => 'Music reviews filterable by genre',

'supports' => array( 'title', 'editor', 'author', 'thumbnail', 'trackbacks', 'custom-fields', 'comments', 'revisions', 'page-attributes' ),

'taxonomies' => array( 'genres' ),

'public' => true,

'show_ui' => true,

'show_in_menu' => true,

'menu_position' => 5,

'menu_icon' => 'dashicons-format-audio',

'show_in_nav_menus' => true,

'publicly_queryable' => true,

'exclude_from_search' => false,

'has_archive' => true,

'query_var' => true,

'can_export' => true,

'rewrite' => true,

'capability_type' => 'post'

);

register_post_type( 'music_review', $args );

}

add_action( 'init', 'register_cpt_music_review' );

function genres_taxonomy() {

register_taxonomy(

'genres',

'music_review',

array(

'hierarchical' => true,

'label' => 'Genres',

'query_var' => true,

'rewrite' => array(

'slug' => 'genre',

'with_front' => false

)

)

);

}

add_action( 'init', 'genres_taxonomy');

The only line that changed was the 'taxonomies' => array('genre') line within our custom post type. I added this line to tell our custom post type to connect to our new taxonomy and use it instead of the default category or tag structure WordPress comes installed with.
If you’ve made it this far you can now visit your WordPress admin area and see your new custom post type and taxonomy(Genres) present. Congrats!

Our custom post type and taxonomy are successfully implemented. Here we can add a new Music Review which contains various types of genres decided upon by the user.

Getting Our Code To Output

Below I’ll try adding a new music review. You should see the new Genres section that we set up with our custom Taxonomy. With some data entered I’ll publish the post.

Create a new music review as an example.

At this point we have our functionality set up within our plugin.
In order to make things effortless we will rely on the plugin to create a new page called Music Reviews. The page will be referenced by our plugin and output any new music reviews the user posts. We are doing this so the user doesn’t have to edit a single line of code.

Tying it All Together

Our code now works but we should create a page that will use

// Function used to automatically create Music Reviews page.

function create_music_review_pages()

{

//post status and options

$post = array(

'comment_status' => 'open',

'ping_status' =>  'closed' ,

'post_date' => date('Y-m-d H:i:s'),

'post_name' => 'music_review',

'post_status' => 'publish' ,

'post_title' => 'Music Reviews',

'post_type' => 'page',

);

//insert page and save the id

$newvalue = wp_insert_post( $post, false );

//save the id in the database

update_option( 'mrpage', $newvalue );

}

And finally we need to create our Music Reviews page once the plugin is activated. Adding the code below initiates the function we just wrote above ( function create_music_review_pages(){…}).

// // Activates function if plugin is activated

register_activation_hook( __FILE__, 'create_music_review_pages');

Testing

Our plugin should be ready to test at this point. Lets create an example music review and see what outputs.

Create another music review to verify our plugin is working correctly.

If you click View Music Review once the post is published you should be taken to a screen which looks similar to the image below. Your theme and styles may vary…

The single page music review template

You may notice that I modified the menu to include our new Music Reviews page. Doing this gives us easy access.

Adjusting primary navigation to include “Music Reviews” page

With your menu in place and saved click on Music Reviews to see all the posts we have made so far.
Based on the page template supplied by your theme the Music Review should output all together and be clickable through to the single review template. You will probably notice that the music review I posted earlier has output as well as the one we just created.

Our music reviews on the “Music Review” page

Our feature image, title, genre, and review all have posted successfully. Our plugin works!
To verify, you can deactivate the plugin and reinstall it or activate it. Upon doing so a new Page called Music Reviews should be created. You can delete or reuse the one from before if there are duplicates but there should be only one “Music Reviews” page. We could have added a function to delete and restore this page within our plugin but I wanted to keep things as simple as possible.

Finish

Our plugin is a relatively simple one. You can extend it so much further by including it’s own predefined templates, custom widgets, more taxonomies and so much more. Creating a plugin is no easy feat. You will want to plan your plugin before even moving to development. Knowing what you can an can’t do with WordPress before coding your own plugin is a crucial step to developing a quality one. The plugin create in this tutorial is meant to teach by example. There are better standards to follow and more useful practices to endure. Be sure to read the WordPress Codex and get familiar with the WordPress Plugin API. If a plugin isn’t out there and you need custom functionality for your website then I stronger encourage trying to create your own!