<?php

$input = array(1,1,1,2,2,3,3,4,5,5);
$parts = array_count_values($input);

print_r($parts);

foreach ($parts as $key => $val) {
    $parts[$key] = array_fill(0, $val, $key);
}

print_r($parts);

?>

Array
(
    [1] => 3
    [2] => 2
    [3] => 2
    [4] => 1
    [5] => 2
)
Array
(
    [1] => Array
        (
            [0] => 1
            [1] => 1
            [2] => 1
        )

    [2] => Array
        (
            [0] => 2
            [1] => 2
        )

    [3] => Array
        (
            [0] => 3
            [1] => 3
        )

    [4] => Array
        (
            [0] => 4
        )

    [5] => Array
        (
            [0] => 5
            [1] => 5
        )

)