php.net |  support |  documentation |  report a bug |  advanced search |  search howto |  statistics |  random bug |  login

go to bug id or search bugs for

Bug #79843 Running intval to string value that is supposed to be INF returns 0
Submitted: 2020-07-13 09:46 UTC Modified: 2020-07-15 09:46 UTC
From: taira dot 815 dot terashima at gmail dot com Assigned: cmb (profile)
Status: Not a bug Package: Strings related
PHP Version: 7.4.8 OS: Ubuntu18.04
Private report: No CVE-ID: None
View Developer Edit
Welcome back! If you're the original bug submitter, here's where you can edit the bug or add additional notes.
If you forgot your password, you can retrieve your password here.
Password:
Status:
Package:
Bug Type:
Summary:
From: taira dot 815 dot terashima at gmail dot com
New email:
PHP Version: OS:

 

 [2020-07-13 09:46 UTC] taira dot 815 dot terashima at gmail dot com 
Description:
------------
Running function intval using a string value more than a certain number (maybe DOUBLE MAX) returns 0.

Test script:
---------------
<?php
// It returns 0. (This string value is 2^1024)

$number = intval('179769313486231570772930519078902473361797697894230657273430081157732675805500963132708477322407536021120113879871393357658789768814416622492847430639474124377767893424865485276302219601246094119453082952085005768838150682342462881473913110540827237163350510684586298239947245938479716304835356329624224137216');

echo $number;

Expected result:
----------------
INF

Actual result:
--------------
0

Patches

Pull Requests

History

AllCommentsChangesGit/SVN commitsRelated reports
 [2020-07-13 09:59 UTC] cmb@php.net 
For numbers exceeding PHP_INT_MAX, intval() is supposed to return
PHP_INT_MAX; see <https://3v4l.org/tf7EJ>.
 [2020-07-15 01:13 UTC] taira dot 815 dot terashima at gmail dot com 
Oh, I see.
Sorry, One digit missing.
If Add 0 to number's last, result were 0.
 [2020-07-15 01:14 UTC] taira dot 815 dot terashima at gmail dot com 
See this.
<https://3v4l.org/1Pi3j>
 [2020-07-15 07:46 UTC] nikic@php.net 
@cmb: float -> int conversion does not perform a saturating cast, it performs a truncating cast. A good way to think of it is that we first cast the float to a bigint and then cast the bigint to a smaller integer size. As usual with integer casts, this will simply take the low bits and discard the high bits. The same happens with float -> int casts, just with more thorny details ;)
 [2020-07-15 09:46 UTC] cmb@php.net
-Status: Open +Status: Not a bug -Assigned To: +Assigned To: cmb
 [2020-07-15 09:46 UTC] cmb@php.net 
Thanks for the explanation, @nikic.

Anyhow, the PHP manual says[1]:

| If the float is beyond the boundaries of integer (usually +/-
| 2.15e+9 = 2^31 on 32-bit platforms and +/- 9.22e+18 = 2^63 on
| 64-bit platforms other than Windows), the result is undefined,
| since the float doesn't have enough precision to give an exact
| integer result. No warning, not even a notice will be issued when
| this happens!

[1] <https://www.php.net/manual/en/language.types.integer.php#language.types.integer.casting.from-float>
 
PHP Copyright © 2001-2025 The PHP Group
All rights reserved. 		Last updated: Tue Mar 11 06:01:29 2025 UTC