php 5.3 — Как преобразовать число в строку (букву) в php?

Вот пример ….

<form method='POST' action="<?php echo htmlspecialchars($_SERVER['PHP_SELF']);?>" >
Enter the Number:
<input type="number" max="999999999" name="number" required="required">(max value:999999999)<br/><input type="submit" value="Submit" name="Submit"><br/></form>
<?php
if(isset($_POST['Submit'])){
class N2L{
var $number  = array( 0 => 'zero',1 => 'one',2 => 'two',3  => 'three', 4 => 'four',5 => 'five',6 => 'six',7 => 'seven',
8 => 'eight',9 => 'nine',10 => 'ten',11 => 'eleven',12 => 'twelve',13 => 'thirteen',14 => 'fourteen',
15 => 'fifteen',16 => 'sixteen',17 => 'seventeen',18 => 'eighteen',19 => 'nineteen',20 => 'twenty',
30 => 'thirty',40 => 'forty',50 => 'fifty',60 => 'sixty',70 => 'seventy',80 => 'eighty',90 => 'ninety',
100 => 'hundred',1000 => 'thousand',100000 => 'lakh',10000000 => 'crore');

function index($numb){
if($numb<100){
return $this->upto_99($numb);
}elseif($numb<1000){
return $this->upto_999($numb);
}elseif($numb<100000){
return $this->upto_99999($numb);
}elseif($numb<10000000){
return $this->upto_9999999($numb);
}else{
return $this->upto_999999999($numb);
}
}
function upto_999999999($numb){
$number=  $this->number;
if($numb<=200000000){
$crores=(int)($numb/10000000);
$str=" ".$number[$crores]." ".$number[10000000];
}else{
$crores=(int)($numb/100000000)*10;
$crores_odd=(int)($numb%100000000)/10000000;
$str=" ".$number[$crores]." ".$number[$crores_odd]." ".$number[10000000];
}

$tens_old=(int)($numb%10000000);
$str.=" ".$this->upto_9999999($tens_old);

return " ".$str;

}

function upto_9999999($numb){
$number=  $this->number;
if($numb<=2000000){
$lakhs=(int)($numb/100000);
$str=" ".$number[$lakhs]." ".$number[100000];
}else{
$lakhs=(int)($numb/1000000)*10;
$lakhs_odd=(int)($numb%1000000)/100000;
$str=" ".$number[$lakhs]." ".$number[$lakhs_odd]." ".$number[100000];
}

$tens_old=(int)($numb%100000);
$str.=" ".$this->upto_99999($tens_old);

return " ".$str;

}
function upto_99999($numb){
$number=  $this->number;
if($numb<=20000){
$thousands=(int)($numb/1000);
$str=" ".$number[$thousands]." ".$number[1000];
}else{
$thousands=(int)($numb/10000)*10;
$thousands_odd=(int)($numb%10000)/1000;
$str=" ".$number[$thousands]." ".$number[$thousands_odd]." ".$number[1000];
}

$tens_old=(int)($numb%1000);
$str.=" ".$this->upto_999($tens_old);

return " ".$str;

}

function upto_999($numb){
$number=  $this->number;
if($numb>99 && $numb<1000){
$hundreds=(int)($numb/100);
$str=" ".$number[$hundreds]." ".$number[100];
$tens_old=(int)($numb%100);
$str.=" ".$this->upto_99($tens_old);

return " ".$str;
}

}
function upto_99($numb){
$number=  $this->number;
if($numb>20 && $numb<100){
$tens=(int)($numb/10)*10;
$units=$numb%10;
return $number[$tens]." ".$number[$units];
}
else{
return " ".$number[$numb];
}
}
}
$leter=new N2L();

echo "The number ".$_POST['number']." in Words is ".$leter->index($_POST['number']);}

?>