Register Shortcode

If you want to add shortcodes in your plugin you can :

1. Create a Shortcodes folder

Shortcodes/

2. Add the abstract class Shortcode.php

<?php

namespace BEA\PB\Shortcodes;

/**
 * This class is the base class of Shortcode
 * It have to be used as base for all Shortcodes
 *
 * Class Shortcode
 *
 * @package BEA\PB\Shortcodes
 * @since   2.1.0
 */
abstract class Shortcode {

	/**
	 * The shortcode [tag]
	 * @var string
	 * @since   2.1.0
	 */
	protected $tag = '';

	/**
	 * List of supported attributes and their defaults
	 *
	 * @var array
	 * @since   2.1.0
	 */
	protected $defaults = [];

	/**
	 * Create a shortcode
	 *
	 * @since   2.1.0
	 */
	public function add(): void {
		add_shortcode( $this->tag, [ $this, 'render' ] );
	}

	/**
	 * Combine the attributes gives us whit defaults attributes
	 *
	 * @since   2.1.0
	 *
	 * @param array $attributes
	 *
	 * @return mixed
	 */
	public function attributes( $attributes = [] ) {
		return shortcode_atts( $this->defaults, $attributes, $this->tag );
	}

	/**
	 * Display shortcode content
	 *
	 * @since   2.1.0
	 *
	 * @param array $attributes
	 * @param string $content
	 *
	 * @return string
	 */
	abstract public function render( $attributes = [], $content = '' );

}

3. Add the Shortcode Factory class

<?php

namespace BEA\PB\Shortcodes;

/**
 * The purpose of this factory is to create shortcodes easily
 *
 * The usage of the class is something like this :
 *
 * Shortcode_Factory::register( 'My_Shortcode_Class' );
 *
 * My_Shortcode_Class have to be a child of Shortcode class
 *
 * Class Shortcode_Factory
 *
 * @package BEA\PB\Shortcodes
 * @since   2.1.0
 */
class Shortcode_Factory {

	/**
	 * Instantiate a shortcode with the given class
	 * Do not specify the namespace
	 *
	 * @param string $class_name : Shortcode the Shortcode ClassName to register
	 *
	 * @return Shortcode|\WP_Error Instance of the Shortcode added or false on failure
	 * @since 2.1.0
	 */
	public static function register( string $class_name ) {
		$class_name = __NAMESPACE__ . '\\' . $class_name;
		if ( empty( $class_name ) || ! class_exists( $class_name ) || ! is_subclass_of( $class_name, Shortcode::class ) ) {
			return new \WP_Error( 'fail_shortcode_registration', sprintf( 'Fail to instantiate shortcode %s', $class_name ) );
		}

		/**
		 * Since the shortcodes are Singleton we only have to get the instance
		 * and call the add method
		 *
		 * @var Shortcode $class
		 */
		try {
			/** @psalm-suppress UnsafeInstantiation */
			$class = new $class_name();
			$class->add();
		} catch ( \Exception $e ) {
			return new \WP_Error( 'fail_shortcode_instanciation', sprintf( 'Fail to instantiate shortcode with error %s', $e->getMessage() ) );
		}

		return $class;
	}
}