bash-4.3$ php -r 'function e($a){foreach($a as$i=>$v){if($v)break;unset($a[$i]);}return array_reverse($a);}print_r(e(e(explode(",",$argv[1]))));' -- '0,0,4,2,1,0,0,1,2,4,0,0'
Array
(
    [0] => 4
    [1] => 2
    [2] => 1
    [3] => 0
    [4] => 0
    [5] => 1
    [6] => 2
    [7] => 4
)