roundcubemail/program/lib/Roundcube/rcube_plugin.php
public function register_handler($name, $callback)
    {
        $this->api->register_handler($name, $this->ID, $callback);
    }
public function register_handler($name, $callback)
    {
        $this->api->register_handler($name, $this->ID, $callback);
    }
public function register_handler ( $ name , $ callback ) { $ this -> api -> register_handler ( $ name , $ this -> ID , $ callback ) ; }
Register a handler function for a template object

When parsing a template for display, tags like <roundcube:object name="plugin.myobject" />
will be replaced by the return value if the registered callback function.

@param string $name     Object name (should be unique and start with 'plugin.')
@param mixed  $callback Callback function as string or array with object reference
and method name
Register a handler function for a template object