Month: October 2019

WordPress plugins are used to extend the functionality of a WordPress website. There are about 51,000+ plugins available in WordPress’s official plugins repository at the writing of this post. There are scenarios when you need to develop your own WordPress plugin for some specific task/requirement. In this blog post, we present some useful functions, hooks, filters, and best practices for custom WordPress plugin development.

Built-In Functions:

wp_email('example@example.com', 'Subject', 'Message');
wp_die('The message here');

function_exists() - for functions
isset() - for variables
class_exists() - for classes
defined() - for constants

is_admin()
is_singular()
is_page()
is_archive()

//data validation
is_email() // check if email is valid
term_exists() checks if term exists
username_exists() checks if the username exists

//data sanitization
sanitize_email()
sanitize_text_field()
sanitize_user() // sanitize data as username

//nonces
wp_nonce_field('myplugin_form_action', 'myplugin_nonce_field', false);
wp_verify_nonce($nonce, 'myplugin_form_action');

Pluggable Functions:

https://codex.wordpress.org/Pluggable_Functions

Wp Security Techniques:

Plugin Security

• Data Validation
• Sanitizing input – make sure input is safe
• Sanitizing output – make sure output is safe
• Using nonces – make sure submitted forms are secure
• Checking users

Best Practices:

• File organization
• Plugin architecture
• Avoid naming collisions
• Choose a good name for your plugin
• Write great documentation
• Plugin boilerplates

Common Best Practices:

• Add blank index files in each directory of the plugin so that the contents of the plugin directories are not directly accessible (excluding the images, css and js folders)
• Make sure to check the constant ABSPATH is defined to prevent direct access to the PHP files of the plugin

Hooks:

Example

function myplugin_action_hook_example(){
    wp_email('example@example.com', 'Subject', 'Message');
}
add_action('init', 'myplugin_action_hook_example');

References:
https://codex.wordpress.org/Plugin_API/Action_Reference  

Important Hooks

register_activation_hook() // runs when the plugin is activated
if(! current_user_can('activate_plugins')) return;
//do things like adding options, creating tables etc.
register_deactivation_hook() // runs when the plugin is deactivated
if(! current_user_can('activate_plugins')) return;
//do things like 
flush_rewrite_rules();

register_uninstall_hook() // runs when the plugin is uninstalled
if(! current_user_can('activate_plugins')) return; 
//do things like
delete_option('myplugin_posts_per_page', 10); 

Filters:

function myplugin_filter_hook_example($content){
    $content = $content . '<p>Custom Content Here...</p>';
    return $content;
}
add_filter('the_content', 'myplugin_filter_hook_example');

References:
https://codex.wordpress.org/Plugin_API/Filter_Reference 

This post describes the exact step to develop a custom WordPress plugin from scratch using Object-Oriented Programming.

Go to https://wppb.me/, fill the form and download your zip file

Edit the main file (plugin-name.php) and update texts like ‘description’ if you want

Create all custom post types, make sure that the custom post type title is not longer than 20 characters otherwise you will get an error ‘invalid post type’

function create_post_uni_lms_classes_std() {
    register_post_type( 'uni_lms_classes',
        array(
            'labels' => array(
                'name' => __('Classes','unilms'),
                'singular_name' => __('Class','unilms'),
                'add_new' => __('Add New','unilms'),
                'add_new_item' => __('Add New Class','unilms'),
                'edit' => __('Edit','unilms'),
                'edit_item' => __('Edit Class','unilms'),
                'new_item' => __('New Class','unilms'),
                'view' => __('View','unilms'),
                'view_item' => __('View Class','unilms'),
                'search_items' => __('Search Classes','unilms'),
                'not_found' => __('No Class found','unilms'),
                'not_found_in_trash' => __('No Classes found in Trash','unilms'),
                'parent' => __('Parent Class','unilms')
            ),

            'public' => true,
            'menu_position' => 15,
            'supports' => array( 'title' ),
            'taxonomies' => array( '' ),
            'has_archive' => true,
            'show_in_menu' => false
        )
    );
}

add_action( 'init', 'create_post_uni_lms_classes_std' );

Create a menu page for plugin settings or configurations by using add_menu_page() and add_submenu_page() functions

function uni_lms_admin_actions_std(){
add_menu_page(
	__('Problems We Solve Enhancement', $this->plugin_name),
	'Problems We Solve',
	'edit_posts',
	$this->plugin_name,
	array( $this, 'display_dashboard_page' ),
	'dashicons-admin-settings',
	30
);

add_submenu_page(
	$this->plugin_name,
	__('Success Stories', $this->plugin_name),
	'Success Stories', 'edit_posts',
	'edit.php?post_type=success-stories'
);
}
add_action('admin_menu', 'uni_lms_admin_actions_std');