Singleton trait

Singleton.php

<?php
trait Singleton {

	/**
	 * @var static $instance
	 */
	protected static $instance;

	/**
	 * @return static
	 */
	public static function getInstance() {
		if ( empty( self::$instance ) ) {
			self::setInstance( new self() );
		}

		return self::$instance;
	}

	/**
	 * @param static $instance
	 */
	protected static function setInstance( $instance ) {
		self::$instance = $instance;
	}
}