Advent of code 2015/10

Ajax Direct

function solve($num, $count)
{
    $a = [
        "111" => "a",
        "11"  => "b",
        "1"   => "c",
        "222" => "d",
        "22"  => "e",
        "2"   => "f",
        "333" => "g",
        "33"  => "h",
        "3"   => "i",
    ];

    $b = [
        "a" => "31",
        "b" => "21",
        "c" => "11",
        "d" => "32",
        "e" => "22",
        "f" => "12",
        "g" => "33",
        "h" => "23",
        "i" => "13",
    ];

    for ($i = 0; $i < $count; $i++) {
        $c   = str_replace(array_keys($a), array_values($a), $num);
        $num = str_replace(array_keys($b), array_values($b), $c);
    }

    return strlen($num);
}

$solution_1 = solve((string) $input, 40);
$solution_2 = solve((string) $input, 50);