PHP Error Handling and Magento Developer Mode

You have installed new module but Magento is not executing your code neither throwing any error just try to run Magento in developer mode.
You can turn on the developer mode in .htaccess file or index.php by adding the below line

#File: .htaccess
SetEnv MAGE_IS_DEVELOPER_MODE “”
or
#File: index.php
if (isset($_SERVER['MAGE_IS_DEVELOPER_MODE'])) {
Mage::setIsDeveloperMode(true);
}

This will ensure that Magento will throw exception even for Warning and Notices
Please visit link for more detail: http://alanstorm.com/magento_exception_handling_developer_mode