"update notice" for self-hosted themes

update-notice.php

<?php

function pfun_update_notification ( $transient ) {

	if ( empty( $transient->checked['pfun'] ) ) {
	    return $transient;
	}

	$url = 'http://ptheme.com/update.json';
	//Send the request.
	$result = wp_remote_get($url);
	$code = wp_remote_retrieve_response_code($result);
	$body = wp_remote_retrieve_body($result);
	$data = json_decode( $body, true );
	
	if ( ($code == 200) && !empty($body) ){
		if( version_compare( $transient->checked['pfun'], $data['pfun']['new_version'], '<' ) )
 		$transient->response['pfun'] = (array) $data['pfun'];
	}
 	return $transient;
}
add_filter ( 'pre_set_site_transient_update_themes', 'pfun_update_notification' );