CODEWITHSUNDEEP
phpcastingintegertype-conversion
Niklas R
Niklas R

Reputation: 16870

Convert a big integer to a full string in PHP

I've been searching for a while now, but what I can find is not what I search for. I need to convert an integer value, that may be very huge, to a string. Sounds easy: "$var"? No, because this can lead to the E+ representation of the number.

<?php

$var = 10000000000000000000000000;
echo $var."\n";
echo "'$var'\n";
echo (string) $var."\n";
echo strval($var);

?>


1.0E+25
'1.0E+25'
1.0E+25
1.0E+25

How can I make the output be 10000000000000000000000000 instead?

Upvotes: 9

Views: 13952

Answers (4)

Binh Le
Binh Le

Reputation: 353

I'm facing this problem when getting facebook id and find it in MySQL. And after half hour, i found this work perfectly! Insert this line to your php script:

ini_set('precision',30);

From: https://forums.phpfreaks.com/topic/125907-solved-convert-big-number-to-string/#entry651084

Upvotes: 4

hakre
hakre

Reputation: 197767

The integer number you like to express:

$var = 10000000000000000000000000;

is not available on your system. It's too large and therefore PHP converts it into a float which will change the number (32 bit system example):

       10000000000000000905969664

Common limits are:

 yours :  10 000 000 000 000 000 000 000 000
 32 bit:                       2 147 483 648
 64 bit:           9 223 372 036 854 775 808

The change of the value is called floating point precision, the PHP manual about integers will tell you about the integer limit and the floats page about floating point precision (see the big red warning). Depending on which system you are, you can compile PHP with the ranges your application needs or you must use another datatype, for example with the gmp library which is able to pick strings as integer numbers and handle them.

The following example shows just output, but you can do multiplications etc.:

$r = gmp_init('10000000000000000000000000');
echo gmp_strval($r);

Hope this is helpful.

Upvotes: 2

kingmaple
kingmaple

Reputation: 4310

This is not stored as an integer by PHP, but a float, this is why you end up with 1.0E+25 instead of 10000000000000000000000000.

It's sadly not possible to use that as an integer value in PHP, as PHP cannot save an integer of that size. If this comes from database then it will be a string and you can do with it whatever you want. If you store it elsewhere then store it as a string.

Your alternative is to store it as a float and take that into account at all times, though that requires additional conversions and handling in places.

It's also been suggested to use GNU Multiple Precision, but that's not enabled in PHP by default.

$int=gmp_init("10000000000000000000000000");
$string=gmp_strval($int);
echo $string;

Upvotes: 9

Ofir Baruch
Ofir Baruch

Reputation: 10356

UPDATE: Found the next post:

// strval() will lose digits around pow(2,45);
echo pow(2,50); // 1.1258999068426E+015
echo (string)pow(2,50); // 1.1258999068426E+015
echo strval(pow(2,50)); // 1.1258999068426E+015

// full conversion
printf('%0.0f',pow(2,50)); // 112589906846624
echo sprintf('%0.0f',pow(2,50)); // 112589906846624

Use printf or sprintf.

Upvotes: 5

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