base_url() getting error in code igniter 1.7.3

Install Code igni开发者_如何转开发tor 1.7.3 and try to convert my existing project which is in 1.7.1 but getting Call to undefined function base_url()

You probably replaced your autoload.php with the default one in config.php, so now you are not automatically loading url_helper.

$autoload['helper'] = array('url');

Please try to set the the variable in the config/config.php $config['base_url']