Warning: Massive error in json_encode()

Question

<?php  
$int = 1968401665333658496;  
echo json_encode( array("$int",$int) );  
?>

Recieved in browser: [ "1968401665333658496" , 1968401665333658600 ]

It "rounds off" my integer?

Btw : PHP_INT_MAX = 9223372036854775807 ~ PHP Version 5.3.2-1ubuntu4.7
No problems with these huge integers anywhere (PHP, MySQL or Javascript)
- until json_encode() screws it up (silently btw..)

score 4 · Answer 1 · edited May 23 '17 at 12:11

4

It's not just a JSON issue. If you put

alert(1968401665333658496);

in firebug console you get 1968401665333658600

You're probably hitting the JS max value.

There's a discussion on that here : What is JavaScript's highest integer value that a Number can go to without losing precision?

edited May 23 '17 at 12:11

Community

1
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answered Apr 04 '11 at 17:00

JohnP

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OK, I may have been a bit hasty, claiming "no problem" in javascript :) – T4NK3R Apr 04 '11 at 17:23

score 2 · Accepted Answer · answered Apr 04 '11 at 17:05

2

Javascript has no concept of integers, according to the standard all numbers are IEEE doubles, which means they have 52 bits of mantissa. this leads to a practical maximum "integer" value of 2^53 before any loss of precision.

I am not sure how you didn't have problems with numbers this large in JS alone - if you didn't your JS implementation is not standards compliant.

answered Apr 04 '11 at 17:05

tobyodavies

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Wow, that's sobering. Having worked professionally with JS, not knowing such a basic fact. Still 2^53 = 9007199254740992, still leaves me plenty of wriggleroom for my (8 types of) unique-key scheme : ) THANK YOU! – T4NK3R Apr 04 '11 at 17:28

score 1 · Answer 3 · answered Apr 04 '11 at 16:58

1

Quote your integer value and handle the conversion on the client.

answered Apr 04 '11 at 16:58

Diodeus - James MacFarlane

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this will not help at all - this number is larger than what a standards compliant JS implementation can handle without loss of precision. – tobyodavies Apr 04 '11 at 17:05
If you knew it wouldn't make any difference why did you suggest it? – tobyodavies Apr 05 '11 at 03:12
1

OP doesn't need an INT it's a "unique key scheme", don't see why it can't be a string. – James Oct 25 '11 at 12:44
If you need big integers, you can handle the conversion on the client: http://jsfromhell.com/classes/bignumber – Diodeus - James MacFarlane Oct 25 '11 at 13:27
That truly looks like JS from HELL - good to know this class exists. Thank you Diodeus – T4NK3R Jan 31 '14 at 14:30

Warning: Massive error in json_encode()

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