Convert Number To Words

<?php
function numtowords($num){
	$ones = array( 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");
	
	$tens = array( 2 => "twenty",3 => "thirty",4 => "forty",5 => "fifty",6 => "sixty",
				   7 => "seventy",8 => "eighty",9 => "ninety");
	
	$hundreds = array("hundred","thousand","million","billion","trillion","quadrillion"); //limit t quadrillion
	
	$num = number_format($num,2,".",",");
	$num_arr = explode(".",$num);
	$wholenum = $num_arr[0];
	$decnum = $num_arr[1];
	$whole_arr = array_reverse(explode(",",$wholenum));
	krsort($whole_arr);
	$rettxt = "";
	foreach($whole_arr as $key => $i){
		if($i < 20){
			$rettxt .= $ones[$i];
		}
		elseif($i < 100){
			$rettxt .= $tens[substr($i,0,1)];
			$rettxt .= " ".$ones[substr($i,1,1)];
		}else{
			$rettxt .= $ones[substr($i,0,1)]." ".$hundreds[0];
			$rettxt .= " ".$tens[substr($i,1,1)];
			$rettxt .= " ".$ones[substr($i,2,1)];
		}
		if($key > 0){
			$rettxt .= " ".$hundreds[$key]." ";
		}
	}
	if($decnum > 0){
		$rettxt .= " and ";
		if($decnum < 20){
			$rettxt .= $ones[$decnum];
		}elseif($decnum < 100){
			$rettxt .= $tens[substr($decnum,0,1)];
			$rettxt .= " ".$ones[substr($decnum,1,1)];
		}
	}
	return $rettxt;
}

echo "45436997.25 = ". numtowords("45436997.25");
?>