foreach ($customers as $key => $value) {
Edit: Also, I don't think your "print" statement will do what you think it will. If you want to echo the element value followed by the key, do something like this:
echo $value . ' is ' . $key;
The below does not print anything.
It would if you turned on error reporting/display, and you'd also have a lot more insight into what your scripts are doing.