PHPUnit: assert two arrays are equal, but order of elements not important

What is a good way to assert that two arrays of objects are equal, when the order of the elements in the array is unimportant, or even subject to change?

The cleanest way to do this would be to extend phpunit with a new assertion method. But here's an idea for a simpler way for now. Untested code, please verify:

Somewhere in your app:

 /**
 * Determine if two associative arrays are similar
 *
 * Both arrays must have the same indexes with identical values
 * without respect to key ordering 
 * 
 * @param array $a
 * @param array $b
 * @return bool
 */
function arrays_are_similar($a, $b) {
  // if the indexes don't match, return immediately
  if (count(array_diff_assoc($a, $b))) {
    return false;
  }
  // we know that the indexes, but maybe not values, match.
  // compare the values between the two arrays
  foreach($a as $k => $v) {
    if ($v !== $b[$k]) {
      return false;
    }
  }
  // we have identical indexes, and no unequal values
  return true;
}

In your test:

$this->assertTrue(arrays_are_similar($foo, $bar));