Taking large integer input in PHP

Question

I want to take integer input in PHP but the integer can be up to 10^12

<?php

$input = fopen('php://stdin', "r");
fscanf($input, "%d", $x);
print $x;
?>

The above code do not works for input after 10^10.How can we take this integer input?Here is the link

You can use a float instead - floats are precise for integers up to 2^51, which is far, far more than the 10^12 you need. You can then do validation to ensure it's an integer value, etc. — Niet the Dark Absol
– Niet the Dark Absol, Commented Jun 4, 2014 at 10:58
Because 10^12 > 2^31. But if you have the 64-bit version of PHP then you're all set because 10^12 ≪ 2^63 — Niet the Dark Absol
– Niet the Dark Absol, Commented Jun 4, 2014 at 11:34

deceze · Accepted Answer · 2014-06-04 11:01:01Z

3

Well yes, you cannot have an int beyond a certain limit (depending on 32 or 64 bit platform). Your alternative is to use a float instead, but this is unsuitable if you require absolute precision. The other alternative is to keep the number as string, and operate on it as string using the bc math functions.

$number = file_get_contents('php://stdin');
if (!ctype_digit($number)) {
    trigger_error("$number is not a number");
}
echo $number;
echo bcadd($number, 42);

answered Jun 4, 2014 at 11:01

deceze♦

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3 Comments

Niet the Dark Absol Over a year ago

+1 for bc math, but floats do have absolute precision for integers up to the size of the mantissa ;)

deceze Over a year ago

@Niet So, they are precise, unless they aren't...? ;)

Niet the Dark Absol Over a year ago

Hehe, fair point. They're precise under certain circumstances, which is generally good enough for me - although I've learned to always use things like += 0.125 rather than += 0.1 when expecting exact results.

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