Here we are discussing about how to get logged in customer details.Below code shows how we can achieve that

   $customerData = Mage::getSingleton('customer/session')->getCustomer();
   $cdata=$customerData->getData();

Before using this code make sure to check whether a user is logged in or not by this code

if(Mage::getSingleton('customer/session')->isLoggedIn()):
  //code
endif;

As a whole the code look like this

if(Mage::getSingleton('customer/session')->isLoggedIn()):
   $customerData = Mage::getSingleton('customer/session')->getCustomer();
   $cdata=$customerData->getData();
endif;

The variable $cdata will return the array consisting of the required details

So by using this code we can get logged in customer details