wp_autoupdate.php

<?php
if( !class_exists( 'wp_auto_update' ) ) {
	class wp_auto_update
	{
		/**
		 * The plugin current version
		 * @var string
		 */
		private $current_version;

		/**
		 * The plugin remote update path
		 * @var string
		 */
		private $update_path;

		/**
		 * Plugin Slug (plugin_directory/plugin_file.php)
		 * @var string
		 */
		private $plugin_slug;

		/**
		 * Plugin name (plugin_file)
		 * @var string
		 */
		private $slug;

		/**
		 * License User
		 * @var string
		 */
		private $license_user;

		/**
		 * License Key 
		 * @var string
		 */
		private $license_key;

		/**
		 * Initialize a new instance of the WordPress Auto-Update class
		 * @param string $current_version
		 * @param string $update_path
		 * @param string $plugin_slug
		 */
		public function __construct( $current_version, $update_path, $plugin_slug, $license_user = '', $license_key = '' )
		{
			// Set the class public variables
			$this->current_version = $current_version;
			$this->update_path = $update_path;

			// Set the License
			$this->license_user = $license_user;
			$this->license_key = $license_key;

			// Set the Plugin Slug	
			$this->plugin_slug = $plugin_slug;
			list ($t1, $t2) = explode( '/', $plugin_slug );
			$this->slug = str_replace( '.php', '', $t2 );		

			// define the alternative API for updating checking
			add_filter( 'pre_set_site_transient_update_plugins', array( &$this, 'check_update' ) );

			// Define the alternative response for information checking
			add_filter( 'plugins_api', array( &$this, 'check_info' ), 10, 3 );
		}

		/**
		 * Add our self-hosted autoupdate plugin to the filter transient
		 *
		 * @param $transient
		 * @return object $ transient
		 */
		public function check_update( $transient )
		{
			if ( empty( $transient->checked ) ) {
				return $transient;
			}

			// Get the remote version
			$remote_version = $this->getRemote_version();

			// If a newer version is available, add the update
			if ( version_compare( $this->current_version, $remote_version->new_version, '<' ) ) {
				$obj = new stdClass();
				$obj->slug = $this->slug;
				$obj->new_version = $remote_version->new_version;
				$obj->url = $remote_version->url;
				$obj->package = $remote_version->package;
				$transient->response[$this->plugin_slug] = $obj;
			}
			return $transient;
		}

		/**
		 * Add our self-hosted description to the filter
		 *
		 * @param boolean $false
		 * @param array $action
		 * @param object $arg
		 * @return bool|object
		 */
		public function check_info($false, $action, $arg)
		{
			if (isset($arg->slug) && $arg->slug === $this->slug) {
				$information = $this->getRemote_information();
				return $information;
			}
			return false;
		}

		/**
		 * Return the remote version
		 * @return string $remote_version
		 */
		public function getRemote_version()
		{
			$params = array(
				'body' => array(
					'action' => 'version',
					'license_user' => $this->license_user,
					'license_key' => $this->license_key,
				),
			);
			$request = wp_remote_post ($this->update_path, $params );
			if ( !is_wp_error( $request ) || wp_remote_retrieve_response_code( $request ) === 200 ) {
				return unserialize( $request['body'] );
			}
			return false;
		}

		/**
		 * Get information about the remote version
		 * @return bool|object
		 */
		public function getRemote_information()
		{
			$params = array(
				'body' => array(
					'action' => 'info',
					'license_user' => $this->license_user,
					'license_key' => $this->license_key,
				),
			);
			$request = wp_remote_post( $this->update_path, $params );
			if (!is_wp_error( $request ) || wp_remote_retrieve_response_code( $request ) === 200 ) {
				return unserialize( $request['body'] );
			}
			return false;
		}

		/**
		 * Return the status of the plugin licensing
		 * @return boolean $remote_license
		 */
		public function getRemote_license()
		{
			$params = array(
				'body' => array(
					'action' => 'license',
					'license_user' => $this->license_user,
					'license_key' => $this->license_key,
				),
			);
			$request = wp_remote_post( $this->update_path, $params );
			if ( !is_wp_error( $request ) || wp_remote_retrieve_response_code( $request ) === 200 ) {
				return unserialize( $request['body'] );
			}
			return false;
		}
	}
}