How to get data from Magento System Configuration

Solution 1:

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

sectionName, groupName and fieldName are present in etc/system.xml file of your module.

The above code will automatically fetch config value of currently viewed store.

If you want to fetch config value of any other store than the currently viewed store then you can specify store ID as the second parameter to the getStoreConfig function as below:

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

Solution 2:

you should you use following code

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

Mage::app()->getStore() this will add store code in fetch values so that you can get correct configuration values for current store this will avoid incorrect store's values because magento is also use for multiple store/views so must add store code to fetch anything in magento.

if we have more then one store or multiple views configured then this will insure that we are getting values for current store

Solution 3:

Magento 1.x

(magento 2 example provided below)

sectionName, groupName and fieldName are present in etc/system.xml file of the module.

PHP Syntax:

Mage::getStoreConfig('sectionName/groupName/fieldName');

From within an editor in the admin, such as the content of a CMS Page or Static Block; the description/short description of a Catalog Category, Catalog Product, etc.

{{config path="sectionName/groupName/fieldName"}}

For the "Within an editor" approach to work, the field value must be passed through a filter for the {{ ... }} contents to be parsed out. Out of the box, Magento will do this for Category and Product descriptions, as well as CMS Pages and Static Blocks. However, if you are outputting the content within your own custom view script and want these variables to be parsed out, you can do so like this:

<?php
    $example = Mage::getModel('identifier/name')->load(1);
    $filter  = Mage::getModel('cms/template_filter');
    echo $filter->filter($example->getData('field'));
?>

Replacing identifier/name with the a appropriate values for the model you are loading, and field with the name of the attribute you want to output, which may contain {{ ... }} occurrences that need to be parsed out.

Magento 2.x

From any Block class that extends \Magento\Framework\View\Element\AbstractBlock

$this->_scopeConfig->getValue('sectionName/groupName/fieldName');

Any other PHP class:

If the class (and none of it's parent's) does not inject \Magento\Framework\App\Config\ScopeConfigInterface via the constructor, you'll have to add it to your class.

// ... Remaining class definition above...

/**
 * @var \Magento\Framework\App\Config\ScopeConfigInterface
 */
protected $_scopeConfig;

/**
 * Constructor
 */
public function __construct(
    \Magento\Framework\App\Config\ScopeConfigInterface $scopeConfig
    // ...any other injected classes the class depends on...
) {
  $this->_scopeConfig = $scopeConfig;
  // Remaining constructor logic...
}

// ...remaining class definition below...

Once you have injected it into your class, you can now fetch store configuration values with the same syntax example given above for block classes.

Note that after modifying any class's __construct() parameter list, you may have to clear your generated classes as well as dependency injection directory: var/generation & var/di