How to Build a Carousel Slider Plugin for WordPress

Posted on 21st June 2023

In this tutorial, we will show you how to build a carousel slider plugin for WordPress. A carousel slider is a great way to showcase products, images, or videos on your WordPress site.

There are a few carousel slider plugins available for WordPress, but in this tutorial, we will show you how to build your own.

Building a WordPress plugin can seem like a daunting task, but with a little planning and some basic PHP and JavaScript knowledge, it’s actually quite easy.

In this tutorial, we will walk you through the process of building a carousel slider plugin for WordPress step-by-step.

Step 1: Planning Your Plugin

The first step in building any WordPress plugin is to plan your plugin. You need to decide what your plugin will do, what features it will have, and how it will work.

For our carousel slider plugin, we will keep it simple and include the following features:

A shortcode to insert the carousel into posts and pages

An options page to configure the carousel

The ability to add unlimited images to the carousel

The ability to set the title, caption, and link for each image

The ability to select the size of the carousel

Once you have an idea of what your plugin will do, you need to come up with a name and a slug for your plugin. The name is what will be displayed to users, while the slug is the unique identifier for your plugin.

For our plugin, we will use the name “Carousel Slider” and the slug “carousel-slider”.

Step 2: Creating the Plugin Files

Now that we have planned our plugin, it’s time to start creating the files. In your WordPress plugin development folder, create a new folder for your plugin.

For our plugin, we will create a folder called “carousel-slider”.

Inside your plugin folder, you need to create two files:

The main plugin file: This is the file that WordPress will load when your plugin is activated. This file must have the same name as your plugin folder and be located in the root of your plugin folder. For our plugin, the file will be called “carousel-slider.php”.

The second file is an optional file called “readme.txt”. This file is not required, but it is a good idea to include it in your plugin. The readme file is used to provide information about your plugin, such as the name, description, author, version, etc.

Step 3: Creating the Plugin Header

The first thing you need to do in your main plugin file is to create the plugin header. The plugin header is a comment block at the top of the file that contains information about your plugin.

The plugin header is required and must contain the following information:

Plugin Name: The name of your plugin.

Plugin URI: The URL of your plugin’s website.

Description: A short description of your plugin.

Version: The current version number of your plugin.

Author: The author of your plugin.

Author URI: The URL of the author’s website.

Text Domain: The unique identifier for your plugin. This is used for internationalization.

Domain Path: The relative path to the translation files.

Network: Whether your plugin can only be activated on a network or not.

License: The license your plugin is released under.

License URI: The URL of the license your plugin is released under.

The plugin header for our carousel slider plugin will look like this:

Step 4: Registering the Plugin Settings

Next, we need to register our plugin settings. Plugin settings are options that are saved in the WordPress database and can be retrieved and updated by your plugin.

In our carousel slider plugin, we will register two plugin settings:

carousel_slider_settings: This is an array that will hold all of our plugin settings.
carousel_slider_image_sizes: This is an array of image sizes that our plugin will use.

We will register our plugin settings using the WordPress function register_setting(). This function takes three arguments:

The name of the setting. This must be unique and should be prefixed with your plugin slug to avoid conflicts.
The name of the group the settings are saved in. This should be your plugin slug.
The callback function to sanitize and validate the settings.

Our plugin settings will be registered in the “carousel-slider” group and we will use the carousel_slider_sanitize_settings() function to sanitize and validate our settings.

We will define the carousel_slider_sanitize_settings() function later in this tutorial.

Step 5: Creating the Plugin Options Page

Now that we have registered our plugin settings, we need to create an options page where users can configure the settings.

We will use the WordPress function add_options_page() to add our plugin options page. This function takes four arguments:

The page title.
The menu title.
The capability required to view the page.
The slug of the page.

We will set the page title to “Carousel Slider”, the menu title to “Settings”, the capability to “manage_options”, and the slug to “carousel-slider”.

The add_options_page() function also takes a fifth argument, which is the callback function that will render the page. We will define the carousel_slider_render_options_page() function later in this tutorial.

Step 6: Rendering the Plugin Options Page

Now that we have registered our plugin settings and added an options page, we need to write the code to render the page.

The callback function that we defined in the add_options_page() function, carousel_slider_render_options_page(), is where we will put the code to render our plugin options page.

This function will use the WordPress function settings_fields() to output the hidden fields and nonce for our plugin settings.

Next, we will use the WordPress function do_settings_sections() to output the sections and fields for our plugin settings.

Finally, we will use the WordPress function submit_button() to output the “Save Changes” button for our plugin settings.

Step 7: Registering Plugin Settings Sections

Now that we have the code to render our plugin options page, we need to register the sections for our settings.

Sections are used to group related settings together. Our carousel slider plugin will have two sections:

General Settings: This section will contain general settings for the plugin, such as the carousel size.
Image Settings: This section will contain settings for the images in the carousel, such as the title, caption, and link.

We will