Error in convert number to word - php

Question

I am try to convert number to word. so I use below this code. But when convert Some of numbers are show error. Error is "Undefined offset: -4" in line number 47 and 48. how to solve this error. My Code is below
<?php
$total_amount=8123.52;
$number = $total_amount;
$no = round($number);
$point = round($number - $no, 2) * 100;
$hundred = null;
$digits_1 = strlen($no);
$i = 0;
$str = array();
$words = array('0' => '', '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');
$digits = array('', 'hundred', 'thousand', 'lakh', 'crore');
while ($i < $digits_1) {
$divider = ($i == 2) ? 10 : 100;
$number = floor($no % $divider);
$no = floor($no / $divider);
$i += ($divider == 10) ? 1 : 2;
if ($number) {
$plural = (($counter = count($str)) && $number > 9) ? 's' : null;
$hundred = ($counter == 1 && $str[0]) ? ' and ' : null;
$str [] = ($number < 21) ? $words[$number] .
" " . $digits[$counter] . $plural . " " . $hundred
:
$words[floor($number / 10) * 10]
. " " . $words[$number % 10] . " "
. $digits[$counter] . $plural . " " . $hundred;
} else $str[] = null;
}
$str = array_reverse($str);
$result = implode('', $str);
$points = ($point) ?
"." . $words[$point / 10] . " " .
$words[$point = $point / 10] : '';
echo $result . "(Approx)" ;
?>

Answer 1

Problem is in fourth line $point = round($number - $no, 2) * 100;. It throws error when subtraction give minus output.
try something like this
$point = round($no - $number, 2) * 100 ;
if($point < 0 ){
$point = $point * (-1);
}
And problem solved.