4.20. Sorting an Array Using a Method Instead of a Function

4.20.1. Problem

You want to define a custom sorting routine to order an array. However, instead of using a function, you want to use an object method.

4.20.2. Solution

Pass in an array holding a class name and method in place of the function name:

usort($access_times, array('dates', 'compare'));

4.20.3. Discussion

As with a custom sort function, the object method needs to take two input arguments and return 1, 0, or -1, depending if the first parameter is larger than, equal to, or less than the second:

class pc_sort {
    // reverse-order string comparison
    function strrcmp($a, $b) {
        return strcmp($b, $a);
    }
}

usort($words, array('pc_sort', 'strrcmp'));

4.20.4. See Also

Chapter 7 for more on classes and objects; Recipe 4.18 for more on custom sorting of arrays.