spl_autoload_register Throws an Error in My Production Server

[eluser]Aken[/eluser]
Just because it works in one environment doesn't guarantee it'll work in another. Maybe there's a path not being set correctly, or an issue of case (in)sensitivity. Unless you can guarantee that the environments are the same, you risk having bugs like this sometimes. But the error is saying that Frontend_Controller does not exist, which means the file was not correctly included, which leads me to believe that the autoload function didn't work as expected. Do some debugging.

And that definitely explains your first error, so yeah. Upgrade your PHP version if you can, because anonymous functions are awesome.