<code>
if ( !class_exists('ThemeUpdateChecker') ):
    
class ThemeUpdateChecker {
    public $theme = '';              
    public $metadataUrl = '';        
    public $enableAutomaticChecking = true; 
    
    protected $optionName = '';      
    protected $automaticCheckDone = false;
    protected static $filterPrefix = 'tuc_request_update_';
                                         
    public function __construct($theme, $metadataUrl, $enableAutomaticChecking = true){
        $this->metadataUrl = $metadataUrl;
        $this->enableAutomaticChecking = $enableAutomaticChecking;
        $this->theme = $theme;
        $this->optionName = 'external_theme_updates-'.$this->theme;
        
        $this->installHooks();        
    }
        
    public function installHooks(){
        
        if ( $this->enableAutomaticChecking ){
            add_filter('pre_set_site_transient_update_themes', array($this, 'onTransientUpdate'));
        }
        
        
        add_filter('site_transient_update_themes', array($this,'injectUpdate')); 
        
    
        add_action('delete_site_transient_update_themes', array($this, 'deleteStoredData'));
    }
    
    
    public function requestUpdate($queryArgs = array()){
        
        $queryArgs['installed_version'] = $this->getInstalledVersion(); 
        $queryArgs = apply_filters(self::$filterPrefix.'query_args-'.$this->theme, $queryArgs);
        
    
        $options = array(
            'timeout' => 10,
        );
        $options = apply_filters(self::$filterPrefix.'options-'.$this->theme, $options);
        
        $url = $this->metadataUrl; 
        if ( !empty($queryArgs) ){
            $url = add_query_arg($queryArgs, $url);
        }
        
        
        $result = wp_remote_get($url, $options);
        
        
        $themeUpdate = null;
        $code = wp_remote_retrieve_response_code($result);
        $body = wp_remote_retrieve_body($result);
        if ( ($code == 200) && !empty($body) ){
            $themeUpdate = ThemeUpdate::fromJson($body);
            
            if ( ($themeUpdate != null) && version_compare($themeUpdate->version, $this->getInstalledVersion(), '<=') ){
                $themeUpdate = null;
            }
        }
        
        $themeUpdate = apply_filters(self::$filterPrefix.'result-'.$this->theme, $themeUpdate, $result);
        return $themeUpdate;
    }
    

    public function getInstalledVersion(){
        if ( function_exists('wp_get_theme') ) {
            $theme = wp_get_theme($this->theme);
            return $theme->get('Version');
        }

    
        foreach(get_themes() as $theme){
            if ( $theme['Stylesheet'] === $this->theme ){
                return $theme['Version'];
            }
        }
        return '';
    }
    
    
    public function checkForUpdates(){
        $state = get_option($this->optionName);
        if ( empty($state) ){
            $state = new StdClass;
            $state->lastCheck = 0;
            $state->checkedVersion = '';
            $state->update = null;
        }
        
        $state->lastCheck = time();
        $state->checkedVersion = $this->getInstalledVersion();
        update_option($this->optionName, $state); //Save before checking in case something goes wrong 
        
        $state->update = $this->requestUpdate();
        update_option($this->optionName, $state);
    }
    
    
    public function onTransientUpdate($value){
        if ( !$this->automaticCheckDone ){
            $this->checkForUpdates();
            $this->automaticCheckDone = true;
        }
        return $value;
    }
    

    public function injectUpdate($updates){
        $state = get_option($this->optionName);
        
        
        if ( !empty($state) && isset($state->update) && !empty($state->update) ){
            $updates->response[$this->theme] = $state->update->toWpFormat();
        }
        
        return $updates;
    }
    

    public function deleteStoredData(){
        delete_option($this->optionName);
    } 
    
    
    public function addQueryArgFilter($callback){
        add_filter(self::$filterPrefix.'query_args-'.$this->theme, $callback);
    }
    
    
    public function addHttpRequestArgFilter($callback){
        add_filter(self::$filterPrefix.'options-'.$this->theme, $callback);
    }
    
    public function addResultFilter($callback){
        add_filter(self::$filterPrefix.'result-'.$this->theme, $callback, 10, 2);
    }
}
    
endif;

if ( !class_exists('ThemeUpdate') ):

class ThemeUpdate {
    public $version;     
    public $details_url;  
    public $download_url; 
        
    public static function fromJson($json){
        $apiResponse = json_decode($json);
        if ( empty($apiResponse) || !is_object($apiResponse) ){
            return null;
        }
        
        
        $valid = isset($apiResponse->version) && !empty($apiResponse->version) && isset($apiResponse->details_url) && !empty($apiResponse->details_url);
        if ( !$valid ){
            return null;
        }
        
        $update = new self();
        foreach(get_object_vars($apiResponse) as $key => $value){
            $update->$key = $value;
        }
        
        return $update;
    }
        
    public function toWpFormat(){
        $update = array(
            'new_version' => $this->version,
            'url' => $this->details_url,
        );
        
        if ( !empty($this->download_url) ){
            $update['package'] = $this->download_url;
        }
        
        return $update;
    }
}
    
endif;
</code>

<code>$example_update_checker = new ThemeUpdateChecker(  
    'yefengs',  //这个是主题的名字   
    'http://xxxx.com/update.json' //这个地址是主题检查更新的地址,他是一个json文件链接
);  </code>

<code>{
    "version" : "1.4.3",
    "details_url" : "http://xxooxxoo.com/details.html",
    "download_url" : "http://xxooxxoo.com/yefengs.zip"
}</code>