<?php 

$myarray = array(2,1,2,'',2,1,2,'',2,1,2,1,1,2,1,2,'',2,1,2,'',2,1,2,1,2);
$tests = array_chunk($myarray, 13);
//print_r($tests);

function mytest($tests)
{
    foreach($tests as $test) 
    {
        // play your test !
        print_r(array_count_values($test));
    }    
}
// add your argument for your test
echo mytest($tests);
?>

Array
(
    [2] => 6
    [1] => 5
    [] => 2
)
Array
(
    [2] => 7
    [1] => 4
    [] => 2
)