Magento. Create block.

mage_create_block.md

    /**
     * First way (1) use layout for block create
     */
    $block = Mage::app()->getLayout()->createBlock('customermenu/page_html_header_menu')
                                     ->setTemplate('customermenu/page/html/header/menu.phtml')
                                     ->toHtml();
                                     
    /**
     * First way (2) use layout for block create
     * Need setTemplate() in block __construct()
     */
    $block = Mage::app()->getLayout()->createBlock('customermenu/page_html_header_menu')
                                     ->toHtml();


    /**
     * Second way use core method getBlockSingleton()
     * Need setTemplate() in block __construct()
     */
    $block = Mage::getBlockSingleton('customermenu/page_html_header_menu')
                    ->toHtml();

    /**
     * Second way use core method getBlockSingleton() with setTemplate()
     */
    $block = Mage::getBlockSingleton('customermenu/page_html_header_menu')
                    ->setTemplate('customermenu/page/html/header/menu.phtml')
                    ->toHtml();