Fastest way to check if an array is sorted

Question

Considering there is an array returned from a function which is of very large size.

What will be the fastest approach to test if the array is sorted?

Answer 1

This might not be the fastest but it's the complete solution. Every value with index lower than i is checked against the current value at i. This is written in php but can easily be translated into c# or javascript

for ($i = 1; $i < $tot; $i++) {
        for ($j = 0; $j <= $i; $j++) {
            //Check all previous values with indexes lower than $i
            if ($chekASCSort[$i - $j] > $chekASCSort[$i]) {
                return false;
            }
        }
    }