class conversion number to word

[ekowk]

Dear All PHP Master,
Kindly need your help (I'm sorry my Bad English), I'm new in PHP and OOP in PHP please help to check I have class to convert number to words below, but when I'm running it the result in browser is error with error message :
  Notice: Undefined variable: str in C:\xampp\htdocs\latihan\oop.php on line 16
  Notice: Undefined variable: str in C:\xampp\htdocs\latihan\oop.php on line 14
  Notice: Undefined variable: str in C:\xampp\htdocs\latihan\oop.php on line 16
  seratus dua puluh tiga juta empat ratus lima puluh enam ribu tujuh ratus delapan puluh sembilan

here it's my code to convert number to words :
<?php 
   Class Terbilang {

      Public function terbilang() {
         $this->dasar = array(1=>'satu','dua','tiga','empat','lima','enam','tujuh','delapan','sembilan');
         $this->angka = array(1000000000000,1000000000,1000000,1000,100,10,1);
         $this->satuan = array('triliun','milyar','juta','ribu','ratus','puluh','');
      }
      
      Public function eja($n) {
         $i=0;
         while($n!=0){
            $count = (int)($n/$this->angka[$i]);
            if($count>=10) $str .= $this->eja($count). " ".$this->satuan[$i]." ";
            else if($count > 0 && $count < 10)
            $str .= $this->dasar[$count] . " ".$this->satuan[$i]." ";
            $n -= $this->angka[$i] * $count;
            $i++;
         }
         $str = preg_replace("/satu puluh (\w+)/i","\\1 belas",$str);
         $str = preg_replace("/satu (ribu|ratus|puluh|belas)/i","se\\1",$str);
         return $str;
      }
   }
   
   $bilangan = new Terbilang;
   echo $bilangan -> eja(123456789);   //shouldbe show :seratus dua puluh tiga juta empat ratus lima puluh enam ribu tujuh ratus delapan puluh sembilan
?>

[trq]

The error is self explanatory, your are trying to concatenate a value onto an inexistent variable $str. Simply declare $str somewhere before you use it.