Okay, Well I'd just like to say I've found one more function particularly useful when dealing with arrays:

array_map
A handy way to run a function on each element of an array. It saves running a loop, running the function on the element then saving it back to the array.

Result: Each element in the array will have the htmlspecialchars() function run on it. You can use your own custom functions as well, just pass the name in as a string without the brackets. Read more @ php.net