PHP calculating real big/large numbers shows wrong result

Question

According to this wiki page:

37975227936943673922808872755445627854565536638199 × 40094690950920881030683735292761468389214899724061

Result should be:

1522605027922533360535618378132637429718068114961380688657908494580122963258952897654000350692006139

I tested:

<?php
$a = '37975227936943673922808872755445627854565536638199';
$b = '40094690950920881030683735292761468389214899724061';

echo "A: ".$a."\n";
echo "B: ".$b."\n";

$c = $a * $b; 

echo "Result:\n".number_format($c, 0, '', '')."\n";
echo "Expected: \n1522605027922533360535618378132637429718068114961380688657908494580122963258952897654000350692006139";
?>

And I got result:

A: 37975227936943673922808872755445627854565536638199
B: 40094690950920881030683735292761468389214899724061

Result: 1522605027922533518260457400714874678658400574018662242210976145948887793656784833912073618129420288

Expected: 1522605027922533360535618378132637429718068114961380688657908494580122963258952897654000350692006139

Why does PHP show wrong result?

Is there a way to get correct result?

Read more about `PHP_INT_MAX`. https://stackoverflow.com/questions/35169951/php-gives-incorrect-results-when-formatting-long-numbers — mitkosoft, Feb 24 '20 at 08:31
@AksenP Logic: 2+2 should NOT be 3 or 5. If you don't understand the question then why downvote and comment questions? — Cyborg, Feb 24 '20 at 10:16

Cyborg · Accepted Answer · 2020-02-24T10:24:27.500

Some say PHP can't handle such large numbers. But I still don't understand the result PHP outputs seems to be large enough to me, but are NOT correct.

Is there a way to get correct results?

Yes, for PHP 1 line solution (using Python3):

echo exec('python3 -c "print('.$a.' * '.$b.')"');

Results as expected:

1522605027922533360535618378132637429718068114961380688657908494580122963258952897654000350692006139

score 0 · Answer 2 · answered Feb 24 '20 at 09:25

0

There are php functions to perform mathematical functions on numbers which are saved as strings:

have a look at this function

answered Feb 24 '20 at 09:25

Jochen

25
6

PHP calculating real big/large numbers shows wrong result

2 Answers2