Terbilang part 1

<?php
function Terbilang($x)
{
    $abil = array("", "satu", "dua", "tiga", "empat", "lima", "enam", "tujuh", "delapan", "sembilan", "sepuluh", "sebelas");
    if ($x < 12)
        return " " . $abil[$x];
    elseif ($x < 20)
        return $this->Terbilang($x - 10) . " belas";
    elseif ($x < 100)
        return $this->Terbilang($x / 10) . " puluh" . $this->Terbilang($x % 10);
    elseif ($x < 200)
        return " seratus" . $this->Terbilang($x - 100);
    elseif ($x < 1000)
        return $this->Terbilang($x / 100) . " ratus" . $this->Terbilang($x % 100);
    elseif ($x < 2000)
        return " seribu" . $this->Terbilang($x - 1000);
    elseif ($x < 1000000)
        return $this->Terbilang($x / 1000) . " ribu" . $this->Terbilang($x % 1000);
    elseif ($x < 1000000000)
        return $this->Terbilang($x / 1000000) . " juta" . $this->Terbilang($x % 1000000);
}