I have a function(this is exactly how it appears, from the top of my file):
Don't declare function inside a loop (like foreach, for, while...) ! Declare before them.
You should include that file (wherein that function exists) only once. So,
instead of : include ("functions.php");
use: include_once("functions.php");
If none of above helps, before function declaration, add a check to avoid re-declaration:
if (!function_exists('your_function_name')) {
function your_function_name() {
........
}
}