Php Singleton Trait and using it in Class

singleton-trait.php

<?php
/**
 * Singleton trait to implements Singleton pattern in any classes where this trait is used.
 */

trait Singleton {

	protected static $_instance = array();

	/**
	 * Protected class constructor to prevent direct object creation.
	 */
	protected function  __construct() { }

	/**
	 * Prevent object cloning
	 */
	final protected function  __clone() { }

	/**
	 * To return new or existing Singleton instance of the class from which it is called.
	 * As it sets to final it can't be overridden.
	 *
	 * @return object Singleton instance of the class.
	 */
	final public static function get_instance() {

		/**
		 * Returns name of the class the static method is called in.
		 */
		$called_class = get_called_class();

		if ( ! isset( static::$_instance[ $called_class ] ) ) {

			static::$_instance[ $called_class ] = new $called_class();

		}

		return static::$_instance[ $called_class ];

	}

}

/**
 * Class which uses singleton trait.
 */
class SingletonClass {
	use Singleton;
}

// To get the instance of the class.
$instance = SingletonClass::get_instance();