How to count the consecutive duplicate values in an array?

I have an array like this:

$arr = array(1, 1, 1, 2, 2, 3, 3, 1, 1, 2, 2, 3);

I found the function array_count_values(), but it will group all of the same values and count the occurrences without respecting breaks in the consecutive sequences.

$result[1] = 5
$result[2] = 4
$result[3] = 3

How can I group each set of consecutive values and count the length of each sequence? Notice there are two sets of sequences for the numbers 1, 2, and 3.

The data that I expect to generate needs to resemble this:

[1] = 3;
[2] = 2;
[3] = 2;
[1] = 2;
[2] = 2;
[3] = 1;

It can be done simply manually:

$arr = array(1,1,1,2,2,3,3,1,1,2,2,3);

$result = array();
$prev_value = array('value' => null, 'amount' => null);

foreach ($arr as $val) {
    if ($prev_value['value'] != $val) {
        unset($prev_value);
        $prev_value = array('value' => $val, 'amount' => 0);
        $result[] =& $prev_value;
    }

    $prev_value['amount']++;
}

var_dump($result);