How to access a function in block class from phtml?

I am not sure whether the class you mentioned above is a Block or Helper.

If it is Block, you can do:

Mage::getBlockSingleton('class_name/remaining_class_name')->getCheckboxRules();

and if it is Helper:

Mage::Helper('class_name/remaining_class_name')->getCheckboxRules();

Where

• class_name is name of registered class name in Block/Model/Helper in your module. Check config.xml file of the module.

---

For Example:

If you want to use Mage_Core_Block_Template_Facade Block from core/Mage files. You can use:

Mage::getBlockSingleton('core/template_facade');

Where

• core text in the above code can be found from core/Mage/Core/etc/config.xml

  <blocks>  <!-- line#91 in Magento 1.8.0 -->
      <core>
          <class>Mage_Core_Block</class>
      </core>
  </blocks>
  

• From above, Mage_Core_Block can be converted to core

if you want get of function of helper class then we below

For,helper:

Mage::helper('modulename/rest_ofclass')->yourFunction();

That means

For You case: Mage::helper('modulename/rest_ofclass')->yourFunction();

modulename/rest_ofclass

1) modulename depends on helper class deceleration on your config.xml.)

<helpers>
    <modulename>
        <class>Magestore_RewardPoints_Helper</class>
    </modulename>
</helper>

2) rest_ofclass (Magestore_RewardPoints_Helper)rest of class from Block_Spend