Support: Get config value

I have write plugin: misc/myplugin/myplugin.php

PHP:

<?php
class Am_Plugin_Myplugin extends Am_Plugin{
 
    const PLUGIN_STATUS = self::STATUS_PRODUCTION;
    const PLUGIN_REVISION = '0.1';
    function onSetupForms(Am_Event_SetupForms $event){
        $form = new Am_Form_Setup('myplugin');
        $form->setTitle('My plugin');
 
        $fr = $form->addFieldset()->setLabel(___('MyPlugin Setting'));
        $fr->addText('site_url',array('size' => 50))->setLabel(___('Site Url'));
 
        $form->addFieldsPrefix('misc.myplugin.');
        $this->_afterInitSetupForm($form);
        $event->addForm($form);
    }
 
    function getReadme()
    {
        return <<<CUT
Required: input url home page.
CUT;
 
    }
}

After active plugin. Site URL save to successfuly.

• I create theme as documents aMember support (Link).

In layout.phtml of theme. I want get Site URL value of Myplugin plugin. Please advice!​

​

• On file misc/myplugin/myplugin.php. I want write a function get Site URL value. Please advice!

Thanks you support!

Thanks you advice!