Get Customer Group within Magento

Magento is built to work with different groups of users/customers.

You can easily find out what group the customer belongs to by the snippet below.

// Mage_Customer_Session
$session = Mage::getSingleton('customer/session');

// Get the Customer Group ID.
$group_id = $session->getCustomerGroupId();

// Get the Group Name the Customer is part of.
$group_name = Mage::getModel('customer/group')->load($group_id)->getCode();

Note: Customers must be log in.

You can check whether a customer is logged in by simply,
if($session->isLoggedIn()) {

// Customer is logged in

} else {

// Not logged in

}