wp_autoupdate.php

<?php

// Source : https://github.com/CasasoftCH/casawp/blob/master/wp_autoupdate.php

class WP_AutoUpdate 
{
        /**
         * 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->plugin = $this->plugin_slug;
                        $obj->package = $remote_version->package;
                        $obj->tested = $remote_version->tested;
                        $transient->response[$this->plugin_slug] = $obj;
                }
                return $transient;
        }
        /**
         * Add our self-hosted description to the filter
         *
         * @param boolean $false
         * @param array $action
         * @param object $arg
         * @return bool|object
         */
        public function check_info($obj, $action, $arg)
        {
                if (($action=='query_plugins' || $action=='plugin_information') && 
                    isset($arg->slug) && $arg->slug === $this->slug) {
                        return $this->getRemote('info');
                }
                
                return $obj;
        }
        /**
         * Return the remote version
         * 
         * @return string $remote_version
         */
        public function getRemote($action = '')
        {
                $params = array(
                        'body' => array(
                                'action'       => $action,
                                'license_user' => $this->license_user,
                                'license_key'  => $this->license_key,
                        ),
                );
                
                // Make the POST request
                $request = wp_remote_post($this->update_path, $params );
                
                // Check if response is valid
                if ( !is_wp_error( $request ) || wp_remote_retrieve_response_code( $request ) === 200 ) {
                        return @unserialize( $request['body'] );
                }
                
                return false;
        }
}