How to get config variable value in magento.?

To get the config variable value in Magento you must use the below code to get the desired results accordingly.

$configValue = Mage::getStoreConfig('sectionName/groupName/fieldName');

$configValue = Mage::getStoreConfig('sectionName/groupName/fieldName',
 Mage::app()->getStore());

Above both methods work fine and automatically fetch the config value of the current viewed store.

Here sectionName, groupName and fieldName are present in etc/system.xml file of your module. You can also set this config values in modules config.xml file as per the requirements.