is_home() isn't a native php function. It couldn't ever be, and i'm not even going to begin to explain why.
However, At some point, it's probably been written in some script you previously had.
Are you defining this function elsewhere in your codebase? If so, you'll need to use include() to pull the file that defines the function into the script you're working with. It's kinda like writing something like:
This will not work on it's own, but if you have your fucking() function defined in a file like includes/func.fucking.php:
Code:
<? function fucking() { echo "do the bartman"; } ?>
Then you'll be able to use that function.:
Code:
<? include('includes/func.fucking.php'); fucking(); ?>
and then your code would work. But to save on execution time (opening multiple files takes longer), you could do:
Code:
<? function fucking() { echo "do the bartman"; } fucking(); ?>