Bug #66450 [Opn]: Casting E notation strings to floats results in incorrect value
Edit report at https://bugs.php.net/bug.php?id=66450&edit=1
ID: 66450
User updated by: howard at zedcore dot com
Reported by: howard at zedcore dot com
-Summary: Casting extremely large E notation strings to floats
results in incorrect value
+Summary: Casting E notation strings to floats results in
incorrect value
Status: Open
Type: Bug
Package: *Programming Data Structures
Operating System: Debian Gnu/Linux "Wheezy" 7.2
PHP Version: Irrelevant
Block user comment: N
Private report: N
New Comment:
It seems to affect any E notation string being cast to float.
var_dump(exp(10), (string)exp(1), exp(1) == (string)exp(1), exp(1) - (string)exp(1));
Result:
float(2.718281828459)
float(2.718281828459)
bool(false)
float(4.5297099404706E-14)
Previous Comments:
------------------------------------------------------------------------
[2014-01-09 17:40:43] howard at zedcore dot com
Description:
------------
Casting a very large float into a string and back-again results in a different value.
The string representation of both values from var_dump() is the same, and as expected.
Reproducible on PHP 5.4.4 and PHP 5.3.10 (Not able to upgrade to the latest PHP release at work but
I'll try to reproduce at home soon).
Test script:
---------------
var_dump(exp(100), (string)exp(100), exp(100) == (string)exp(100), exp(100) - (string)exp(100));
Expected result:
----------------
float(2.6881171418161E+43)
float(2.6881171418161E+43)
bool(true)
float(0)
Actual result:
--------------
float(2.6881171418161E+43)
float(2.6881171418161E+43)
bool(false)
float(3.5652673131419E+29)
------------------------------------------------------------------------
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Edit this bug report at https://bugs.php.net/bug.php?id=66450&edit=1
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