Can't require mage.php from an interactive shell

I would like to try some code snippets (about to make a script) which uses Magento's models and classes.

The problem is that I get the following error:

fdr@fderose-gtrade:/var/www/globaltrade$ 
f开发者_开发百科dr@fderose-gtrade:/var/www/globaltrade$ php -a 

Interactive shell
php > require  './app/Mage.php';
Fatal error: Class 'Mage' not found in /var/www/globaltrade/app/Mage.php on line 31

Line 31 of Mage.php is the following:

Mage::register('original_include_path', get_include_path());

Does anybody have an idea about what could be the cause? Thank you!

According to php.net

Autoloading is not available if using PHP in CLI interactive mode.

see http://php.net/manual/en/features.commandline.interactive.php for more info (its a note towards the bottom of the description)

At first glance it seems that your issue stems from autoload. When you include your Mage.php file it appears that it then tries to run a php autoload and use the Mage class, but is failing in doing so. It's possible that the way that their autoload is functioning, the paths may not be correct when run from an interactive shell.