'first', 0 => 'second', 7 => 'third', 1 => 'fourth', ]; Assert::same(3, Arrays::getKeyOffset($arr, '1')); Assert::same(3, Arrays::getKeyOffset($arr, 1)); Assert::same(2, Arrays::getKeyOffset($arr, 7)); Assert::same(1, Arrays::getKeyOffset($arr, 0)); Assert::same(0, Arrays::getKeyOffset($arr, '')); Assert::null(Arrays::getKeyOffset($arr, 'undefined'));